The Zensah Elbow Compression Sleeve offers targeted compression that supports the elbow muscle to prevent and provide relief from tennis elbow. The Chevron ribbing enhances forearm support and the moisture wicking and anti-microbial proprietary fabric helps to keep you dry. Use during training, competition and recovery. Size: Small: Bicep 7-10, Forearm 7-9 Medium: Bicep 10-13, Forearm 9-11 Large: Bicep 13-Up, Forearm 11-Up*Note: Measure with the arm extended and relaxed the upper forearm circumference - Approx. 2 below the elbow.