A glorified sleeping bag cover, the B1 Scout is as simple as a bivi bag gets. It has a drawcord around the face, but you can never completely seal the face area and there is no mesh insect screen. The design may be plain, but the B1 Scout's X-tex fabric is decidedly hi-tech.
X-tex fabric has a woven textile face with a coating to make it both waterproof and breathable, with a 50 denier polyester face. 50 denier is a heavy yarn by today's standards, but we consider it important for a mountaineering tent, since the intrinsic strength of fabric is derived primarily from the thickness of the yarn. Unusually we have chosen polyester rather than nylon, as polyester offers superior resistance to UV degradation.
In 2015 Crux introduced it's B1 range of bivi bags: the Scout, the Recce and the Patrol. The B1 Scout is the simplest and lightest in the range, with a drawcord closure that leaves a small area of the face uncovered. The robust B1 Recce can be completely closed over the face. The B1 Patrol is the largest and most sophisticated of the Crux bivi bags, with a stiffened wire-rimmed hood that provides shelter while remaining open.
What sets the B1 range apart is it's X-tex fabric - the same revolutionary fabric used in Crux's X1 series of single wall bivouac tents. Most bivi bags use a fabric with a microporous membrane or coating. These rely on differences in the partial pressure of humidity in the air in order to breathe. They only work however, when the humidity is in the vapour state: once condensation has occurred they cease to breathe. X-tex fabric is different: by combining a PU coating with activated carbon, it is able to absorb water even in the liquid state and still continue to breathe.
- Reviewed by Ultralight Outdoor Gear