For treatment of arthritis, sports injuries, and repetitive strain. Provides support and temporary relief of painful tendons and joints. Unlike traditional heat therapy. ThermaDry is a comfortable, long wearing, go anywhere heat treatment. Helping to keep you active! Tapered back for comfort and fit. Open patella to relieve pressure on knee cap. Fits either knee. Unique three-layer construction; first layer is Hydrolon terry which wicks moisture away from skin to keep you dry and comfortable. Perforated Hypolan blend middle layer is comfortable, cushioned and breathable, provides light compression which helps counteract tissue swelling. Durable nylon outer layer retains body's own heat, to naturally increase blood flow to damaged or painful joints and muscles to help encourage healing and pain relief. Antimicrobial. Medium fits knee 14 - 15 inches (measure knee cap).