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