The Sea to Summit Reactor Midweight Liner is an essential companion for hikers and campers braving the cold outdoors. This liner is engineered with Thermolite Pro Technology, using knitted hollow-core fibers and infrared-absorbing ceramic pigments to reflect body heat, enhancing comfort even in colder conditions. Its stretch-knit fabric ensures a snug fit inside any sleeping bag, with a classic mummy design that allows your arms to stretch freely. The liner offers versatile footbox options, from standard mummy to mummy with drawcord, for ventilation and mobility around camp. Made with Thermolite EcoMade fibers, it doesn't compromise on sustainability while delivering on performance. This liner is set to transform your sleep system, adding warmth and comfort for those cool or cold nights.