Ultralight 30°F/-1°C Going Ultralight doesn't have to mean suffering. We'd rather find a way to shave the weight and innovate on performance, like using Flex technology for our Nitro 30. We build in Flex between the shoulders and knees, so you get the comfort and thermal benefits, while saving precious ounces. Foot Box Venting lets you customize the climate in the lower half of your Nitro, without adding the weight of a full-length zipper. Ultralight speed with full-featured comfort.
For superior comfort and heat retention, Sierra Designs incorporates Flex technology into several insulated jackets and sleeping bags. With elastic built into the baffles of both down and synthetic jackets and bags, Flex technology hugs the body, eliminates dead air space, and keeps warm air close to the body. And beyond just keeping you warmer, Flex jackets and sleeping bags move with you for better mobility and a more comfortable night’s sleep.