Knee Support Standard Small 12.25 13.25 CPAP Accessories Battery backup for guardian alert Two 1 inch urethane Battery backup for guardian alert model 30911 * With Back * Fully Assembled * 600 lb Small * Fits knee circum 25 (measurement taken just under the knee cap while knee is slightly bent) * Thermal support for prevention treatment & rehabilitation of the knee * Provides protection and support against general wear and tear including sprains strains and twisted knees * Anatomically shaped in 3 pieces for more comfort and a better fit * Thermoskin increases elasticity of muscles tendons and ligaments to reduce the risk of injury when under stress and strain * Clinically proven to increase surface skin and subcutaneous temperature between 2 3 degrees F the optimal level to make tendons and muscles more pliable and elastic to provide optimal muscle function