Women's Helium II Jacket S - Ultraviolet. Built for flash-storm protection, the 100% waterproof, super-breathable Helium II weighs an incredibly light 5.5 ounces. An ultra-compressible piece you'll never leave behind, it's so light and packs down so small, you'll forget it's clipped to your harness until you throw it on to ward off a sudden mid-route downpour. Compressible to the size of a granola bar.