The Zeta Bags are designed for big wall bivouacs in damp conditions, with all the advantage of Primaloft insulation and Ultrashell outer fabric. The unique twin front zip system doubles for access and for armholes, while the large optional cowl keeps the weather off. Alternatively, strip down the features to create a straightforward synthetic bag. The Delta Bags are down filled bivi bags, ultralight & small pack-down, for extreme ascents and lightweight nights out on the mountain. These shoulder length (hoodless) bags, can be made “stripped-down” for ultimate weight saving or made with a waterproof shell and cowl for the harsh Bivouac nights.