MediCordz Single Head Harness A great addition to your everyday workout routine Can be used for a wide range of functions X-Small: 18.5-19.6in (46.9-49.8cm) ; Small: 19.6-21.2in (49.8-53.8cm) ; Medium: 21.2-22.4in (53.8-56.9cm) ; Large: 22.4-24.0in (56.9-60.9cm) ; X-Large: 24.0-25.1in (60.9-63.8cm) The Head Harness should fit snugly around head