Kelty sleeping bag liner is made in high-grad material. Mostly, sleeping is from cotton polymer. This material can keep body temperature at normal level, though very difficult during cold or winter season. It is strong material that prevents direct touch between grounds to your skin. Moreover, cotton cannot cause irritation for skin. During sleeping night, you will on bag for long time. If bag’s material is poor quality, you will end up having skin trouble in the morning. Another material is fleece, which similar to sweater. It protects and keeps body warm effectively and thicker than cotton in sleeping bag.