Alpha Direct Fleece (100% recycled polyester) Imported Exceptional Warmth-to-Weight: Available in Regular (7.5oz) and Long (8.5oz) sizes, providing a significant thermal boost to your camping sleeping bag without adding bulk to your pack. Versatile Sizing Options: Choose the Regular (fits up to 6') or Long (fits up to 6'6") to ensure a perfect fit that eliminates cold spots and maximizes comfort in any adult sleeping bag. Polartec Alpha Direct Technology: Utilizes advanced lofted fibers that trap body heat more effectively than traditional fleece while allowing for superior moisture transport and breathability. Moisture-Wicking Performance: The hydrophobic fibers resist absorbing moisture and dry incredibly fast, keeping you comfortable and your backpacking sleeping bag dry throughout the night. Minimalist & Packable: Designed to compress into a tiny sleeping bag stuff sack, this liner is the ultimate space-saving solution for hikers looking to extend their gear's temperature range. Boost your sleep system’s warmth without the weight with the Big Agnes Alpha Direct Fleece Sleeping Bag Liner. Engineered for the serious trekker, this ultralight sleeping bag accessory is made from Polartec Alpha Direct, a high-performance active insulation originally designed for Special Forces. This unique lofted fiber construction provides exceptional thermal regulation and breathability, making it much more efficient than standard fleece. Whether you're using it as a standalone lightweight sleeping bag for warm summer nights or as a high-loft boost for your cold weather sleeping bag, this liner delivers maximum warmth-to-weight performance for any backpacking gear kit.