Sierra Designs knows that a full nights' sleep can make or break an outdoor adventure and we've got the solution! Sierra Designs market leading research has identified restrictive bags as being the number one reason why people sleep restlessly in the backcountry. That's precisely why our Flex™ bags are right for you. They are light, efficient and comfortable; along with moving with you, they also adapt to your shape for thermal efficiency. You will not find a more comfortable, thermally efficient bag anywhere... period!

Flex™ Technology

• Flex™ eliminates constriction, allowing the sleeping bag to move with the user and keeping them warm and comfortable
• Flex™ greatly improves a bag's thermal efficiency
• Technically advanced elastic binding tape is used on the 3-season down Flex™ bags, while we use a lighter proprietary elastic thread in the Ultralight series
• Features up to 8" of expandable baffles in our 3 season bags and 7" of partial Flex™ in our Ultralight bags. Flex™ allows the growth of the bag to expand as and where needed.

Flex™ sleeping bags are manufactured under a license by Mont-Bell, LTD. US Patent #4,888,828