Forty Below® "ZVB" Zone Vapor Barrier Vest

The state of the art Forty Below® ZVB Vest™ is a super lightweight, non-insulated “zone vapor barrier” vest designed to help prevent moisture buildup in your clothing layers between you and your backpack. Say goodbye to that sweaty, soaked-back feeling in your jacket or pack—this vest helps keep you drier and more comfortable during high-output activities.

We invented this unique vest back in the 1980s to solve a common problem in extreme cold and high-altitude climbing. When carrying a backpack, perspiration can build up between your back and your clothing layers—causing down suits, jackets, fleece, or wool mid-layers to become damp. Once down insulation gets wet, it loses much of its warmth and can be extremely difficult to dry, especially on long expeditions. This vest helps manage moisture in that critical zone, making it an ideal tool for those who sweat heavily and need to preserve the insulating power of their layers.

This new version of the 40 Below® Zone Vapor Barrier Vest™ represents the state of the art, featuring advanced lightweight materials and a dynamic fit for maximum performance and comfort. These upgrades make the vest ideal not only for high-altitude and extreme cold climbing, but also for cold-weather endurance athletes—including participants in fat-tire bike races, cross-country ski and snowshoe races, and long-distance events like the Iditarod Trail Invitational, Arrowhead 135, Fat Pursuit, and others around the world.