The Expander liner is made from a premium stretch knit poly-cotton, making it super stretchy and even warmer than a standard cotton weave liner. The stretch properties allow the Expander to move with you as you sleep, vastly increasing comfort and minimising tangles. The anti-microbial treatment keeps bacteria at bay as well as prolonging the life of your liner and sleeping bag. The anti-microbial treatment won't wash out of the liner, and does not use nano-sized particles. The treatment is approved for use by the EPA (USA) and is used in many hospitals. Premium stretch knit fabric that can expand twice its width. Luxuriously comfortable to sleep in. Extends the life of a sleeping bag by keeping it clean Anti-microbial protection keeps liner fresh, hygienic and odour-free Double folded and reinforced seams Easy car, machine washable