This five-star rated mattress topper is eco-friendly, contains ethically sourced and pesticide-free organic bamboo, and is delivered in a recycled & recyclable box.
The Panda mattress topper is one of our favourite budget-friendly toppers available in the UK.
It is made of a gel-infused memory foam (called Hydro-foam™), specifically designed with open-cell cooling technology and heat-sensitive capsules that react to your body temperature to keep you cool.
The memory foam also allows for orthopaedic support and can help relieve neck, back, and hip pain.
The bamboo topper cover is soft and naturally breathable, encouraging airflow. 💨
It is also:
- Naturally antibacterial
- Hypoallergenic
- Sustainable & kind to the environment
The cover is removable and machine-washable up to 40℃. 🛀
Panda is an environmentally-friendly brand.
Individual materials are Oeko-Tex Standard 100 certified, no harmful chemicals are used in dyes, and the topper is REACH-certified.
The topper features an anti-slip layer and elastic corner straps to keep it firmly in place.
The Panda memory foam bamboo mattress topper comes with free delivery and returns, a 30-night risk-free trial period, and a 10-year guarantee.
It is delivered rolled up in a recycled and recyclable box. ♻️
Panda mattress topper | |
Materials: | Gel-infused memory foam |
Depth: | 5 cm (2 inches) |
Trial period: | 30 days |
Guarantee: | 10 years |
Available sizes: | Standard single, small double, UK double, king, and super-king sizes; standard EU single, EU double, EU king, EU emperor |
All foams used in this topper are CertiPUR-certified, ensuring they're free from toxins, heavy metals, dyes, and harmful chemicals.
The Simba Hybrid mattress topper is one of the most unique toppers on the market.
Proudly designed by the British Simba Sleep, the Simba topper features three layers:
- Simba-Pure synthetic latex (2.5 cm / 1 inch)
- 2,500 Aerocoil 20 mm mini pocket springs, enclosed in 100% polyester pockets
- High-resilience Simba-Pure base foam (2 cm / 0.7 inches)
The Simba-Pure foam is CertiPUR-certified and guaranteed to be free from TCPP, phosphates, parabens, biocides and persistent organic pollutants. 🌱
This is a cooling mattress topper as the springs allow for maximum airflow.
The cover with 3D mesh fabric is also ultra-breathable, further enhancing airflow.
This helps with temperature regulation, ensuring you stay cool and fresh all night long. ❄️
Because of its hybrid composition, the Simba topper also feels much firmer than pure foam toppers.
This is great if you just want to add a touch of firmness. 🧱
The Simba topper has an anti-slip base and elasticated straps to keep it firmly in place on your mattress.
The Simba mattress topper comes with free delivery & returns, a 14-day returns policy, and a 1-year guarantee.
Simba Hybrid Mattress Topper | |
Materials: | Synthetic latex, mini pocket springs, Simba-Pure foam |
Depth: | 7 cm (2.7 inches) |
Trial period: | 14-day returns policy (you can try out the topper in these 14 days but this is subject to change) |
Guarantee: | 1 year |
Available sizes: | Single, small double, double, king, super king |
This cooling topper comes with a removable and machine-washable cover.
The Emma Flip Topper has a unique dual-sided design with two foam layers.
These are:
- Comfort side: Airgocell foam
- Support side: ZeroGravity foam
The comfort side is slightly softer, while the support side is a little firmer. 🧸🧱
This makes the Emma mattress topper a great option for sleepers who need a little more variety - or aren't sure if they need more softness or firmness.

The topper also comes with a breathable, cooling cover that is fully machine-washable. ❄️
This is great for hygienic reasons!
Unfortunately, the Emma topper doesn't have any straps to attach it to the mattress. 😨
While a good fitted sheet should keep your topper in place, we much prefer toppers with straps for a tighter fit.
The Emma Flip topper comes with free delivery and returns, a 100-night trial period, and a 10-year guarantee.
Emma Flip mattress topper | |
Composition: | Airgocell memory foam and ZeroGravity cold foam |
Depth: | 5 cm (1.9 inches) |
Trial period: | 100 nights |
Guarantee: | 10 years |
Available sizes: | Double, king, super king |
Conveniently, this topper comes with free delivery & returns, plus a 30-day trial period for you to test if you like it!
The Eve Mattress Topper is a memory foam topper by the proudly British Eve Sleep. 🇬🇧
It features two layers of foam:
- Evecomfort open-cell foam (2 cm / 0.7 inches)
- Ultra-resilient reflex base foam (3 cm / 1.2 inches)
The Evecomfort foam is up to 30x more breathable than traditional memory foam, preventing overheating and helping to keep you cool and comfortable throughout the night.
The Eve topper is CertiPUR-certified and tested to meet both British and European quality standards.
This ensures that your topper is free from toxins and harmful chemicals. 🌱
The 100% polyester top cover carries the Oeko-Tex Class 1 certification and is naturally flame retardant.
It is also machine-washable at 40°C, making this a great choice for people prone to allergies.
The topper features convenient corner straps so you can attach it to your mattress.
The Eve mattress topper is available in all standard UK mattress sizes. 🥳
It comes with free delivery & returns, a 30-day risk-free trial period, and a 3-year warranty.
Eve mattress topper | |
Composition: | Memory foam & reflex foam |
Depth: | 5 cm (2 inches) |
Trial period: | 30 days |
Guarantee: | 3 years |
Available sizes: | Standard single, small double, double, king size, super king |
This hypoallergenic topper has antibacterial properties that eliminate odour whilst providing a more comfortable sleep.
The Bamboo Mattress Topper with Charcoal is a responsive memory foam topper that adds a soft sleeping surface to your mattress.
The antibacterial, anti-allergy topper wicks away moisture and eliminates odours during the night. 💧
The outer cover is also designed with breathable air holes to encourage natural ventilation.
The mattress topper has a unique anti-slip base to help keep it fixed on your mattress. 🙌
The Otty mattress topper comes with a 14-day trial and a year’s guarantee.
Otty Bamboo Mattress Topper With Charcoal | |
Composition: | 3 cm of bamboo memory foam layer with charcoal and a thick knit bamboo & charcoal memory foam infused cover |
Depth: | 5 cm (1.9 inches) |
Trial period: | 14 days |
Guarantee: | 1 year |
Available sizes: | Single, double, king, super king |
The Dual Layer Mattress Topper is a 5-star hotel choice for those that like to sleep in luxury.
The Fine Bedding Dual Layer Mattress Topper is a luxurious choice for an enhanced feeling of comfort.
Made of 100% Smartfil® Microfibre, this topper provides a comfortable and breathable sleep. 💨
The dual layer construction includes a zip to remove the top layer for an easy wash up to 60°C.
Fitted with 35 cm (13.7 inches) elastic straps, this topper will fit onto any type of mattress.
Unfortunately, this mattress topper does not include a sleep trial or warranty period.
Dual Layer Mattress Topper | |
Materials: | 100% Super Soft Microfibre cover & 100% Smartfil® Microfibre filling |
Depth: | Not specified |
Trial period: | 14-day returns policy only |
Guarantee: | N/A |
Available sizes: | Single, double, king, super king |
Unlike most mattress toppers, the Silentnight luxury topper is fully machine-washable at 40℃.
The Silentnight Ultimate Luxury Hungarian Goose Feather & Down Mattress Topper has been designed with affordable luxury in mind.
It combines extra-soft Premium Hungarian goose down with feathers for a quilted luxury feel.
The 100% pure cotton cover is soft, comfortable, and naturally breathable. 💨
This helps to improve airflow to keep you cool and refreshed all night long.
Elastic straps on each corner fit the topper securely to your mattress to prevent movement while you sleep.
The Silentnight goose down mattress topper is hypoallergenic and fully machine-washable at 40℃. 🧺
The Silentnight topper comes with free standard delivery and a 2-year guarantee.
Silentnight Hungarian Goose Down Mattress Topper | |
Materials: | Hungarian goose down & feathers |
Depth: | 3 - 5 cm (1.2 inches - 2 inches) |
Trial period: | None |
Guarantee: | 2 years |
Available sizes: | UK double, king, super king |
This luxurious topper has been designed to mould to the shape of your body, offering the ultimate orthopaedic support.
The Tempur memory foam mattress topper has been designed by the esteemed Tempur brand, using NASA-certified memory foam.
Memory foam adapts perfectly to your body shape, offering sufficient pressure relief and supporting your spine.
The foam retains more heat than other types of foam and will create a warm and cosy sleeping environment.
The dual-sided Tempur Topper 7 comes with a removable soft jersey cover that's machine-washable at 60°C.
This is great for people with hygiene concerns or allergy sufferers. 🤧
The Tempur memory foam topper is quite heavy, coming in at 9.8 kg (21.6 lbs) for the smallest size.
Delivery is free and usually takes place within 2 to 4 weeks. 🚛
The Tempur mattress topper is significantly more expensive than other toppers on the market.
It is a good option if you don't have budgetary constraints, but the other toppers we recommend also offer excellent quality at much better prices.
Tempur Topper 7 | |
Materials: | Memory foam |
Depth: | 7 cm (2.7 inches) |
Trial period: | 100 days |
Guarantee: | 10 years |
Available sizes: | Standard small single, single, double, king size, super king |
What is a mattress topper?
Mattress toppers are all the rage.
But what exactly is a mattress topper?
A mattress topper is a 4 - 10 cm thick removable layer of extra padding that you place on top of your mattress.
Often designed as an additional layer of comfort, mattress toppers change the overall feel of your mattress. 🐑
The exact feel of a topper will depend on the material used (more on this a bit further down).
But, in general, mattress toppers are meant to make a firm mattress softer.
Do you need a mattress topper?
You don't necessarily need a mattress topper.
If you've purchased a high-quality mattress that's perfectly comfy, there's no need to buy a mattress topper.
But if your mattress is just a tad too firm, then a mattress topper can really make a world of difference - especially if you're a side sleeper!
This is because side sleepers often need a little extra cushioning to sleep comfortably.
As a guideline, you may need a mattress topper if:
- You want to make your mattress feel softer.
- You want a warmer sleep - or some more airflow if your actual mattress retains a lot of heat.
- You need more orthopaedic support.
- You share your bed with a partner and need better motion isolation.
- You want to bridge the gap between two single mattresses on one double bed.
We go into the specifics of when a mattress topper can help and when it can't in more detail below. 👇
When should you buy a mattress topper?
A comfortable mattress topper cannot solve all your mattress problems, and there are certainly some instances when buying a mattress topper is the wrong choice.
But, there are many times when purchasing a mattress topper is the perfect solution to your mattress-related problems.
This is great news as it'll save you the cost of having to buy a new mattress. 🥳
So if you need any of the below, a mattress topper is the way to go.

Can a mattress topper make my firm mattress softer?
YES!
This is the number one reason people buy a mattress topper. 🥇
If you have a mattress with high-density foams or quality pocket springs that's still in perfect condition but just a bit too firm, then a mattress topper is a perfect solution.
It's also much cheaper than buying a new mattress. 💰
Mattress toppers of any material can add a top layer of soft cushioning to your mattress.
Memory foam, gel foam, and latex mattress toppers are the softest, while cold foam toppers and hybrid toppers are firmer.
Can a mattress topper provide orthopaedic support?
Mattress toppers can effectively reduce aches and pains and provide overall orthopaedic support if a too-firm mattress is at fault.
If your mattress is too firm for you, your spine won't remain straight while you sleep. 📏
You need a mattress that offers enough support for the lighter parts of your body but still offers enough sinkage for your hips and shoulders.
A mattress topper can provide this extra layer of cushioning to help with spinal alignment.
This is also why mattress toppers are so great for side sleepers.

Memory foam mattress toppers are an excellent choice.
Memory foam adapts well to your body, relieving pressure points and supporting sensitive areas like the lower back and hips.
The most premium memory foam mattress topper on the market is the Tempur mattress topper.
It is very expensive but, if you have the budget available, this is an excellent choice.
Can a mattress topper make me feel warmer or cooler?
Mattress toppers generally allow for a warm and cosy sleeping environment.
This is especially true of memory foam toppers.
Memory foam retains more body heat than other types of foam, so you're more likely to feel snug and comfortable.
You can also purchase cooling mattress toppers with cooling gel, enhanced breathability, and temperature-regulating properties. ❄️
The Simba Hybrid mattress topper is a good option.
These breathable mattress toppers are more suitable for hot sleepers as they won't increase the overall temperature.
But, they're unlikely to have a cooling effect if your actual mattress stores a lot of heat.
If you're a hot sleeper, we'd recommend opting for a pocket sprung mattress from the get-go.
The spaces between the springs allow for natural ventilation channels, keeping the air flowing. 💨
This will ensure you stay cool and comfortable and wake up refreshed.
A hybrid mattress, which combines foams with pocket springs, is also a good option.
One of our all-time favourite hybrid mattresses is the Simba Hybrid.
If you find yourself cold during the night, memory foam would be an excellent choice.
Alternatively, consider an electric blanket for a heated mattress topper to keep you cosy and warm. 🔥
Can a mattress topper be used to combine two single mattresses?
If you've used two single mattresses to form a double bed, you'll be familiar with the annoying gap between them.
A large mattress topper placed over both mattresses can help solve this problem.
Keep in mind, though, that this works best if both partners have similar body types 👩❤️👨
If you've chosen two single mattresses because you and your partner have different support requirements, then a bed bridge is a better option.
You can also opt for a customisable mattress, like the Silentnight Yours & Mine Dual Firmness Mattress.
Here, each partner can specify the firmness and comfort levels of each side of the mattress.
Can a mattress topper ease motion transfer?
Yes, absolutely.
If you're sleeping on an innerspring or hybrid mattress, you're likely to experience some motion transfer.
This means that movements from your partner will be carried through the mattress. 👩❤️👨
Adding a memory foam, polyfoam, or latex topper can decrease motion transfer and help you sleep more comfortably.
These mattress toppers are particularly great for couples.
We particularly like the Panda memory foam mattress topper for this. 🐼
In our tests, it significantly altered the motion transfer of our mattress, resulting in a calmer and more restful sleep.
When should you buy a new mattress instead?
A mattress topper is not a miracle cure-it-all.
Sometimes, the only option is to buy a new mattress. 🤦♂️
If any of the below apply, it's time to read our mattress reviews and invest in a new mattress.
Can a mattress topper help with back pain?
As we've seen above, a mattress topper can help with back pain if a too-firm mattress is at fault.
But if your back pain is caused by a mattress of inferior quality that's too soft, old, worn, or sagging, a mattress topper won't make much of a difference. 😔
Similarly, if a damaged slatted frame is at fault, a mattress topper won't do much good.
Can a mattress topper make my soft mattress firmer?
Unfortunately, a mattress topper cannot add much firmness to your mattress.
Actually, the reverse is true - a mattress topper will generally make any mattress feel softer. 😳
Of course, the exact degree of firmness will depend on the material used in the topper.
Memory foam toppers are the softest, and cold foam toppers are the firmest. 🧱
Hybrid toppers, like the Simba mattress topper, are also a tad firmer.
A firm mattress topper can add some general firmness to your mattress, but it won't be able to completely change the way your bed feels.

If your mattress is too soft, you'll have to buy a new mattress.
If you've purchased a bed-in-a-box mattress and you're still within your trial period, you can return your mattress and exchange it for a firmer model or get a full refund. 📦
Can a mattress topper save my old, worn out, and sagging mattress?
A mattress topper is not a substitute for a new mattress.
It may buy you some time, but if your mattress is old, worn out, or sagging, you absolutely have to replace it.
But, there is some playroom here.
If the comfort layer of your mattress has deteriorated and the surface feels a bit uneven, a good mattress topper can help.
But if the actual support of your mattress has dwindled, you'll have to replace it.
A sagging mattress can put excess pressure on your spine, leading to severe back pain. 😩
Even the best bed topper can't fix this.
If you have an old mattress, it's best to replace it.
We recommend a few of our favourite high-quality mattresses below.
Our favourite UK mattresses:
How to choose your perfect mattress topper
Not all mattress toppers are created equal.
There are some great ones on the market, but there are also some substandard ones available.
If you're on the hunt for a new mattress topper, then consider the following key criteria. 🕵️♀️
Consider the density of individual materials
Density is important when choosing a new mattress, but it's equally important when looking at mattress toppers.
Density indicates the amount of material used during production.
The higher the density, the higher the quality of your mattress topper and the more durable it will be.
We recommend a density of at least 40 - 50 kg/m³. 👍
Density is most important when looking at foam mattress toppers.
Overall firmness
While toppers don't necessarily have a set degree of firmness in the way that mattresses do, the material used still affects how soft or firm the mattress topper is.
As a guideline:
- Most standard mattress toppers are categorised as medium-firm.
- Memory foam toppers tend to be the softest.
- Cold foam toppers are the firmest.
Choose according to your personal needs and sleeping preferences, and pay attention to your body weight and size.
The best mattress topper for side sleepers, back sleepers and stomach sleepers varies per sleeping position.
This means:
- Stomach sleepers need an extra firm mattress topper or mattress.
- Back sleepers need a medium-firm mattress topper
- Side sleepers need a soft mattress topper
Your weight and sensitivity to pressure also contribute to whether you need a soft or hard mattress topper.
How thick should your mattress topper be?
Most mattress toppers are between 4 cm (1.6 inches) and 10 cm (3.9 inches) thick.
The thickness you choose will depend on how much softness you require.
- If you want a little bit more cushioning, a thinner topper will be sufficient.
- If you need lots of additional cushioning and support, an extra thick mattress topper is better.
We wouldn't recommend choosing a topper that's under 4 cm thick.
If you're looking for an extra deep mattress topper, take a look at our thick mattress topper review.
We give you our favourite recommendations for 7 - 10cm mattress toppers.
Mattress topper sizes
Of course, your mattress topper has to fit your mattress perfectly.
But you don't need a made to measure mattress topper to make that happen.
Most mattress toppers are available in all of the standard UK mattress sizes 🇬🇧
These include:
- Mattress topper single: 90 x 190 cm (3’ x 6’3”)
- Small double mattress topper: 120 x 190 cm (4' x 6'3")
- Mattress topper double: 135 x 190 cm (4’6” x 6’3”)
- Mattress topper king size: 150 x 200 cm (5’ x 6’6”)
- Super-king mattress topper: 180 x 200 cm (6’ x 6’6”)
Some mattress toppers, like the Panda memory foam bamboo mattress topper, will also be available in select European sizes. 🇪🇺
If you're using a large mattress topper over two single mattresses, ensure that the topper covers both mattresses.
Simply measure the dimensions (length x width) and choose accordingly.
However, caravan mattress toppers or those designed for travelling may come in smaller sizes designed to fit a compact space.
What material should you choose?
Mattress toppers can be made from a variety of different materials.
You're likely to find everything from memory foam toppers to latex mattress toppers, microfibre down-alternative toppers, and natural choices like organic cotton or wool mattress toppers. 🌱
The material the topper is made from will affect the way it feels.
Be aware that different mattress materials will also influence how hot you sleep.
Some materials, like memory foam, polyfoam, or non-ventilated latex retain more heat than materials like down, feathers or wool.
This can make you feel hotter while sleeping. 🥵
Very soft toppers that allow you to sink in very deeply can also restrict airflow and keep you warmer.
If you're a very hot sleeper, consider your mattress topper choice carefully.
Memory foam mattress toppers
Mattress toppers made of memory foam are very popular.
These offer excellent orthopaedic support, adapting perfectly to your body and creating that body-hugging sensation. 🤗
The best memory foam toppers distribute pressure very well and can noticeably relieve surface muscular tension.
Side sleepers often enjoy memory foam toppers.
Memory foam also isolates motion very well, making it a popular choice for couples as you won't feel your partner move. 👩❤️👨
Overall, they create a soft and warm feeling as memory foam retains more heat than other materials.
You're also likely to find memory foam toppers infused with gel, graphite, copper, or other cooling materials to help regulate temperature.
Our article on the best memory foam mattress toppers can tell you more.
Memory foam mattress toppers are good for: | Soft cushioning, orthopaedic support, warm & cosy feel |
Cold foam mattress toppers
Cold foam toppers are firmer and more temperature-neutral than memory foam toppers.
This is because cold foam has an open-cell pore structure, which enhances breathability and results in a cooler feel. 🧊
Cold foam offers good body support but doesn't offer as much pressure relief as memory foam does.
Cold foam mattress toppers are good for: | Good support, dissipating excess heat and moisture |
Gel mattress toppers
Gel mattress toppers are also very popular.
Unlike memory foam, gel foam quickly bounces back to its original shape, making it particularly suitable for restless sleepers. 🕺
Gel foam also offers pressure-relieving properties and adapts well to the body, offering comfort and support.
Cooling gel mattress toppers are particularly great for people looking for a more temperature-neutral sleep.
Gel foam mattress toppers are good for: | Restless sleepers, effective temperature regulation, pressure relief |
Latex foam mattress toppers
Latex foam toppers are similar to memory foam toppers in that they conform to the body while remaining responsive.
Toppers made of latex foam are characterised by their high point elasticity, even pressure distribution, stability, and durability.
You're likely to experience good pressure relief without sinking in as deeply as you do with memory foam toppers.
Back and stomach sleepers will probably find latex toppers more comfortable than memory foam toppers. 👌
Latex foam is also much cooler than other types of foam, mostly as it's ventilated with small holes to promote airflow.
Latex toppers can be made from natural latex or synthetic latex. 🌱
Like wool mattress toppers, these natural options are often attached to mattresses as an integrated pillow top mattress topper.
Latex mattress toppers are good for: | Soft cushioning, pressure distribution, eco-friendliness |
Other mattress topper materials
In addition to the above-mentioned common mattress topper materials, you can also find mattress toppers made of a range of other materials.
Type of topper | Properties |
Bamboo mattress toppers | These do not retain heat and have hypoallergenic properties. |
Cotton mattress toppers | These are comfortable toppers that adapt well to temperature. |
Water mattress toppers | These are recommended for back problems. |
Air mattress toppers | These are also effective for back problems but less comfortable than water mattress toppers. |
Hybrid mattress toppers | These combine two or more materials. |
Wool, down, or feather mattress toppers | These are usually natural mattress toppers with good temperature regulation. |
How much should a good mattress topper cost?
Mattress toppers come in a wide range of prices.
Cheaper mattress toppers, like IKEA mattress toppers, the Eazzzy topper, or some of the Amazon mattress toppers, will set you back an average of £100 for a double size.
But, it's always worth investing in a high-quality product.
More premium products, like the Simba mattress topper and the Eve mattress topper, can cost closer to £250 - £300 for double size.
High-end quality mattress toppers, like the Tempur Topper, will set you back an average of £850 for a double size!
Our favourite budget-friendly quality option is the Panda memory foam topper.
Mattress topper discount codes
Luxury mattress toppers like Tempur will set you back a quid or two.
However, a mattress topper sale can help you buy within your budget.
You should check seasonable periods such as Easter and Christmas for the best sales.
How do you attach a mattress topper?
The last thing you want is your mattress topper moving around on your bed while you sleep - especially if you're a restless sleeper!
Most quality mattress toppers have elastic bands that allow you to easily attach them to your mattress, keeping them firmly in place. 🥳
But some mattress toppers don't have this.
We really wouldn't recommend buying a mattress topper that doesn't come with straps - it can be super uncomfortable.
But, if your mattress topper doesn't come with straps & you don't want to buy a new one, we'd suggest using a fitted sheet or mattress protector to help you keep your topper in place.
Buy bedding:
How do you wash your mattress topper?
Hygiene is very important.
If you're looking after your mattress, the last thing you want is a mattress topper that's stained and unhygienic.
Some foam mattress toppers turn yellow with age, but most mattress toppers (and mattress pads in general) turn yellow due to sweat stains, dead skin, and general household dirt.
Some mattress toppers, like the Silentnight mattress toppers, are fully machine-washable. 🧺
But, most foam mattress toppers cannot be popped into the washing machine.
That's why we recommend you choose a mattress topper with a removable cover that's machine-washable at a high temperature.
This will remove dirt, kill bacteria and dust mites, and help with allergies. 🤧
If your actual foam topper is stained, you can generally remove individual stains with detergent, a damp cloth, and water.
We'd also highly recommend that you invest in a waterproof mattress protector. 💦
Mattress protectors will safeguard both your mattress and mattress topper against dirt, stains, moisture, and bacteria.
If you protect your mattress topper, it should last you 3 - 5 years.
Our favourite UK mattress protectors:
What is the best mattress topper to buy?
You don't need a mattress topper if you have a high-quality mattress that's perfect for you.
But, if your mattress is a bit too firm or you're looking for additional cushioning, a mattress topper is a good idea 😁
The best mattress topper for you will depend on your:
- Budget
- Preferred sleeping temperature
- Orthopaedic concerns
Or favourite all-rounder is the Panda memory foam bamboo mattress topper, but you won't go wrong with any of the ones we've recommended.
Don't forget that a mattress topper is not a cheat for a new mattress.
If your mattress is old, damaged, or sagging, you'll have to throw it out and get a new one.