The Summerlite 32 Degree Down Sleeping Bag is Western Mountaineering's lightest bag with continuous baffles, ideal for backpacking anywhere from nearby lakes to the faraway alpine. This mummy 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 lofty warmth in moisture-riddled environments.