A sleeping bag liner is a thin cloth. It is used in many huts in the mountains. The dorm rooms (the large dormitories) are usually equipped with simple blankets and pillows that can not be washed after each use. In order to maintain hygiene, guests must bring a hut sleeping bag – almost as bedding. This is also the case in some hostels or accommodations.

In addition, the sleeping bag liner can also be pulled into the normal sleeping bag as an inlay. So, the sleeping bag is protected from sweat. On the other hand, it reinforces the insulation of the sleeping bag -depending on the material of the inlay up to 10 degrees (more on that later).
There are differences not only in terms of material but also in shape, type of closure and headboard.

The Shape

Sleeping bag liners come in two different shapes: rectangular or mummy.
In the rectangular version, you have more legroom – but you have to carry a little more fabric with you. If you are planning on using the sleeping bag liner as an inner sleeping bag for your normal sleeping bag, you should look at its shape. Of course, you can also pull a rectangular liner into a mummy sleeping bag – however, you should keep in mind that the liner is then pretty stuffed and also the advantage of legroom is gone …

The Closure

Some sleeping bag liners get opened like classic sleeping bags at the side, while in other models you can simply crawl in from above.
The models with side entry are usually closed with a small velcro.

The Headboard

In general, the headboard is kept simple. However, some versions also have a drawstring in the head opening to adjust the fitting a little bit. In addition, there are sleeping bag liners, which have a slot for the pillow.

The Material

The material, in our opinion, is the aspect you should focus on. Why? Because it will affect your sleep most.

• Cotton
  Regular bed liners are very often made of cotton. So, sleeping bag liners made of this material are most familiar to us at night. In addition to the classic variant, there are also flannel versions. This is roughened cotton, which makes sleeping even more cuddly and keeps you warm. Unfortunately, cotton is a relatively heavy material by nature. In addition to the weight, this has the disadvantage that it dries slowly. There is also a large pack size. Cotton liners are relatively cheap and very resistant. A special kind of cotton is Egyptian cotton. The long-fibered fabric feels cooling on the skin. Since this type of cotton is also very fine, the liner is lighter, dries faster and the pack size is smaller in comparison to other cotton variants. But unfortunately, you have to pay a bit more for these.
  
  
• Silk
  Just like cotton, silk is a raw natural material.
  It has the great advantage of being temperature-regulating: it has an insulating effect when it is cold outside and cools at warm temperatures. In addition, the fine silk fabric causes a very pleasant feeling on the skin. Speaking of fine fabric: silk has a small pack size and is extremely light. As a result, silk dries quickly, even if it is damp or wet. And that’s not all! Silk is slightly antibacterial! This means that even with a longer use without the possibility to wash the liner, you are relatively hygienic. But where is the catch? Um, all these benefits definitely have their price.
  
  
• Silk – Egyptian cotton
  The mixture of the two materials makes the fine silk a bit more resistant and absorbs moisture better. Otherwise, the values for weight, pack size and insulation of the mixed material are approximately between pure silk and Egyptian cotton.
  
  
• Wool
  Woolen inlays are usually made of merino wool. This fabric is temperature regulating similar to​ silk. In cold temperatures, it even provides even more warmth and cuddle feeling and that without scratching! Merino wool is also light, small and quick-drying. Moreover, it does not smell musty so quickly and remains germ-free. From a price point of view, cabin sleeping bags made of merino wool are among the top frontrunners.
  
  
• Synthetic Fiber
  Here, the materials polyester and polyamide are primarily processed as microfiber or fleece. Similar to functional clothing, the lines are breathable and quick-drying. While microfiber also has a small pack size, the variants made of fleece are true pack size monsters … but nice and cuddly. Special materials in the synthetic fiber sector are for example CoolMax and Thermolite. Both fabrics are made of polyester. CoolMax transports moisture even faster, while Thermolite provides the highest insulation through cavities in the fibers.

Another term that can come your way when buying a sleeping bag liner is “silverized“. This means that the artificial fibers were refined with nano-silver. As a result, the fabric does not smell so fast – which is unfortunately often the case with synthetic fiber products.