Western Mountaineering's versatile Tamarak Sleeping Bag transcends the seasons for many different reasons. Obviously it makes an excellent lightweight, two season bag for any adults five feet an under, but it also pairs well with parkas for an alpine bivy system, and the kids will appreciate it for summer camping trips. This semi rectangular bag achieves a phenomenal light weight through its 850 down insulation, the loftiest down available on the market. Western Mountaineering wrapped up this ultralight insulation with a water resistant ripstop material, which Western Mountaineering claims is the lightest downproof fabric out there. The shell's water resistance helps the insulation retain its loft, and warmth, in moisture riddled environments. Western Mountaineering's critical thought to the smallest details makes the Tamarak a long lasting choice. A differential cut places more fabric at the lining to ensure maximum loft inside the bag, and continuous baffles allow you to shift the bag's down toward the top or bottom for more or less warmth. Extra convenient features include a full length zipper on either side, a waterproof stuff sack, and a storage sack with a large volume that helps the bag retain its loft overtime.