Best Sleeping Back Liners
The best sleeping back liners are soft and comfortable against the skin. You should be able to sleep without suffering from irritations. Silk and similar fabrics should work well.
You also want something that is breathable to prevent inside temperatures from soaring. If air can flow freely, then you won’t have to sweat profusely as you sleep. Many are not able to sleep well if they feel hot.
The liner should be light and compact so that it is easy to carry. It should not take too much space inside of your backpack. It should not be a big burden on your shoulders.
Consider the entry points as well. Some are able to open fully with zippers all around the perimeter. This can help in regulating temperature. You will also be able to slide out quickly when going to the bathroom.