When you're backpacking in the high alpine or embarking on some cold weather camping, the Mountain Hardwear Rock Sleeping bag keeps you comfortable in zero degree conditions. Its 650-fill down is light and compresses small into its included stuff sack so you can easily bring it along in your pack. The standard mummy cut efficiently traps your body heat and the draft collar prevents that heat from escaping the bag as you sleep. Additionally, a down-filled face gasket blocks chilly drafts at the hood opening for extra warmth. If you get too warm in the night, the two-way zipper allows you to quickly ventilate and the left and right hand zipper options allow you to zip your bag to a partner's to make a double sleeping bag.