A sleeping bag liner can be a useful accessory. Liners are inserts that do inside a sleeping bag and most are sewn on three sides. There are different styles of liners for different purposes including:
- Warmth: Some liners can increase the temperature range of a sleeping bag
- Cleanliness: Liners protect the sleeping bag from dirt and sweat
- Warm Weather Bag: Warm lines may be able to replace a sleeping bag in very warm conditions
- Comfort: Liners material can be more comfortable than the sleeping bag material
Some liners are made from fabric that is more comfortable than the sleeping bag. Some are designed to add warmth to the sleeping bag. I HIGHLY recommend testing a sleeping bag liner before using it in the outdoors. I purchased a very expensive liner that was supposed to add 25° of warmth and this liner had almost no warmth. Some liners can be very expensive and are just not worth the expense. A warm liner is a good addition to your backpacking equipment. If the weather get unexpectedly cold then it can add warmth to your sleeping bag with minimal weight.