The XCSS Extreme Cold Sleep System was designed to provide exceptional function and warmth in extreme environments. The patent pending LinZip technology has an ergonomic angled zipper to ease closing the bag, while the low-shear closure and unique dropped zipper allow the bag to be split open with little effort in an emergency. The innovative cord management system allows the hood and draft collar to be tightened from inside the bag, preventing heat loss and awkward pulling motions. Adjustment points are also mounted in place, making them easy to find in the dark. All hardware components are field replaceable for reliability during excursions. The XCSS is made of the highest quality materials, offering exceptional performance and durability at only 3.5lbs. The hygiene liner and hydrophobic down both use Celliant® technology, capturing and recycling infrared energy emitted by the human body. This technology is clinically proven to boost tissue oxygen levels, enhance athletic performance, increase heat retention, and improve sleep quality. Overall, the XCSS is a truly unique system, incorporating ergonomics, functionality, fit, thermal efficiency, and comfort.