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We would all love for our outdoor gear to last longer. After all, a camping or trekking setup can easily run hundreds, even thousands of dollars. Perhaps the most undervalued item in your pack is the one you rely on the most. Getting excited about sleeping bags can be difficult when you’ve got gadgets and gizmos galore in your pack. But what if there was a way you could make sure your trusty sleeping bag is still coming with you on trips in ten years’ time?

Sleeping bag liners are one of the most overlooked and underrated pieces of camping equipment — so much so that many hikers and campers go for years without ever using one. For most, though, once they start to use sleeping bag liners, there’s no going back. So what is it that makes these unassuming items worth their weight in gold?

Many campers tend to own just one sleeping bag and rely on it whenever they go camping. These are often three-season sleeping bags, given that they have the broadest temperature range. If you’re heading out in temperatures cooler than your bag is rated to, a sleeping bag liner can add up to 32º to your setup. The warmest sleeping bag liners, like this one from Sea to Summit , often can be used as standalone summer sleeping bags too. Consider how much warmth you need to add when buying a sleeping bag liner because all of those extra degrees do come with a little bulk.

While it’s possible to wash your sleeping bag after every trip, most of the time it just gets opened up, aired out, and packed back into its bag until the next time. Washing a sleeping bag requires space and time, and if you’re camping frequently, you just won’t want to do it. After all, you don’t wash your bedding after every night sleeping in your bed, right? But you also don’t tend to get into your bed in the same state you’re in when you climb into your sleeping bag.

After eight hours of pounding the trails, you’re likely to be covered in sweat, mud, and who knows what else. A quick wash in the creek might help, but you’re still going to be a long way from clean. If you’re using a sleeping bag liner to keep your sleeping bag clean, most people choose a silk liner, like this one from Western Mountaineering , for its comfort, breathability, and light weight. Your sleeping bag liner will protect your sleeping bag from grime and extends its lifespan so that you don’t have to replace your equipment as regularly. When you get home, throw your liner in the wash with your clothes as normal — check the label first, though!

Mountain huts and hostels are a mainstay of hikers and travelers around the world. Because of this, you can guarantee that the bed you’re sleeping in has been used by hundreds of hikers in the past, all in a similar state to how you feel when you crash down onto it. Even if the sheets have been freshly laundered, you’re still in a bed that has some mileage on it. A sleeping bag liner is not only recommended, but many mountain huts in the US insist that guests use them.

In the same way that your sleeping bag liner protects your sleeping bag from you, it can protect you from the bed you’re about to sleep in. This can help you avoid collecting any unwanted clingers on — like bugs — and act as a barrier between you and others who have used the bed in the past. Travelers will often use cotton liners, like this one from REI . Cotton liners are fairly light, breathable, and affordable. In warmer hostels, you can just use a liner and avoid contact with the duvet altogether.

Sleeping bag liners are usually made from cotton, silk, or a synthetic material like polyester.

Cotton liners are the cheapest on the market and are breathable and easy to wash. However, they only add a few degrees of insulation at most, and they’re bulkier than silk. Cotton liners tend to be favored by travelers and budget campers, but they’re a great choice if you want a liner that’s easy to wash. On the trail, these are going to absorb sweat and stain easily, and you can’t wash them on the road and expect them to dry quickly.

Liners made of silk bring a touch of class and elegance to your camping setup. These feel great against your skin, breathe efficiently, pack down small, and make for comfortable standalone sleeping bags in hostels or on warm summer nights. Silk liners are often double the price of cotton liners — if not more — and aren’t as hardwearing either.

Synthetic liners range enormously between models, but they tend to give the most insulation. Fleece liners can comfortably add up to 32º extra warmth to your setup. This can turn your summer sleeping bag into a three-season bag, meaning you don’t have to go out and buy another piece of kit. At the other end of the spectrum, lightweight polyester liners will breathe well and keep you cool on a warm night, especially if you use them without a sleeping bag. Lightweight synthetic liners can have a similar weight and temperature rating to silk, but the more insulated liners will be heavier and bulkier, so you won’t want to carry them if you don’t need to.

In the same way as sleeping bags come in square or mummy shapes, so do sleeping bag liners. The general rule here is that it’s best to get a liner to match the shape of your bag. With the wrong-shape liner, you can end up feeling overly restricted or with a load of leftover material around you. If you’re just looking for a liner to use in a hostel or hut, a square one will make you feel more like you’re in your own bed at home.

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