Solano Mitts Black Diamond NegroThe Black Diamond Solano Mitts deploy supplemental battery powered heat to keep you going lap after lap. Inside, weve upgraded our low profile and fully rechargeable heating system using the premise of countercurrent exchangethe transfer of heat through orienting the heat source perpendicular to the blood flow in the wrist. The heating element now wraps around the inside of the wrist, which increases the mitts warmth and your bodys ability to warm