Traditionally, all of the lightest weight bags are made with the extremely light ripstop nylons. We created our Caribou to be lightweight, durable, and comfortable by using MicroLite XPA'a;"A . This 1 lb. 5 oz. mummy bag has a full length zipper and is cut wider than average for broader shoulders and a more comfortable fit. With its highly breathable taffeta fabric, the Caribou is a durable lightweight summer bag and a great choice for AT hikers. 10 Sewn Thru Box Western Mountaineering Caribou MF Size 5&';6" 6&';0" 6&';6"