The Sine 20F Dridown Sleeping Bag is crafted with high-quality 800 fill power DriDown insulation using hydrophobic-treated down feathers to resist water and retain shape. This down material provides an exceptional balance of lightweight portability and formidable warmth retention. The angled zipper is designed to open with the natural motion of the arm and can be used to provide ventilation as well. A draft tube keeps the heat from leaking out of the zipper, and another angled zipper at the bottom lets you customize ventilation and breathability even further. A built-in pillow pocket lets you store and access goods effortlessly. When it comes to quality and functionality, this sleeping bag is unmatched.