Weighing only 12. 3 ounces, the Sea to Summit Spark Spl Sleeping Bag brings the comfort without the weight whether you're an ultralight backpacker, an adventure racer, a touring bicycler, or an alpine climber. Primarily focusing on giving you the lightest bag out there, Sea to Summit stuffed the Spark Spl with 850 down for the best possible warmth to weight ratio that can still keep you nice and toasty in temps down to 45 F. Sea to Summit utilized Pertex Quantum for the shell to keep the bag as light as possible, and then made the lining out of nylon to keep the bag durable. Going beyond just being ultralight, Sea to Summit's Ultra Dry Down treatment also helps this bag resist moisture to enhance your comfort regardless of the conditions. The Spark Spl has a contoured mummy shape to closely fit your body while you sleep. Its full hood wraps around your head to eliminate the possibility of waking up with freezing ears, and the 13 length zipper on the left helps maximize warmth when the temps drop down to 23 F. The Spark compresses so small that Sea to Summit had to re engineer a new compression sack for it, ending up with a sack that fits in the palm of your hand. So when you get this bag, you might be able to stuff your pack with a few extra snacks for the trip even if you're trying to be as minimalist as possible.