Award-winning for its ultralight prowess, updated with OR's most durable lightweight Helium fabric with Diamond Fuse technology. This clamshell opening bivy is ideal for fast and light missions. The tapered shape of the Helium Bivy works best with tapered shape sleeping pads with narrower dimensions at the foot, ideally 19” or narrower. Ultralight comfort & quick to set up and break down. The Helium Bivy is OR's lightest, best-selling, and most awarded bivy sack of all time. Incredibly quick to set up and breakdown, the ultralight Helium Bivy is 14% lighter than its last generation, and has everything the outdoor minimalist needs to be comfortable. Thru-hikers and bikepackers love the Helium for its refined footprint and reduced weight, and trust it for its durable, lightweight, waterproof Pertex Diamond Fuse technology. A clamshell opening makes it easy to get in, get out, and resists wear and tear for future seasons of adventuring to come. This is the ideal shelter for minimalists who are looking to trade weight for speed, agility, and performance.