Thermicfibre 4 successor after Hollowfibre 4 are spirally twisted polyester fibers, which have four channels. Air holded in this channel causes their excellent isolation properties. Thanks to flexible binding and specific caching to layers, fibers reach so-called LOFT. This means that after unpacking out of the container will take its original volume and fills the space chambers of sleeping bag. Maximum effect and durability is achieved by applying a small layer of silicon on the surface of fibers, which fixes the mutual position of fibers and reduce the mutual friction. Hollow fibers isolate well even in high humidity, do not absorb water, dry quickly, are non-allergic. Easy to maintain and can be washed and dried classically.