Medium * Fits Knee Circum. 13.5 - 15 (measurement Taken Just Under The Knee Cap While Knee Is Slightly Bent) * Elastic Support For Prevention Treatment & Rehabilitation Of The Knee * Thermoskin Elastics Can Expand Contract And Stretch And Are Made Of A High-grade Durable Material That Permits A Full Range Of Movement And Are Comfortable To Wear During A Range Of Activities * Anatomically Designed The Elastic Support Will Comfortably Contour To The Shape Of Your Knee * It Provides Even Compression And Support To Weakened And Injured Knees * It Has Side Stabilizers To Provide Increased Medial And Laterial Support