Summer hiking and trekking involves unpredictable mountain weather. The ARCTERYX Zeta SL Jacket is designed specifically as an emergency shell for hiking. It packs up small so it's ready whenever sudden storms arise. This superlight, packable, emergency waterproof jacket is made from GORE-TEX fabric with Paclite Plus product technology. The minimalist design and fully articulated patterning gives an exceptional fit and freedom of movement.