Twins Special Headgear Head Guard for Protection in Muay Thai, Boxing, Kickboxing, MMA The model HGL-3 is the most comfortable model. It has chin & cheek protection for full contact sparring also provides increased face coverage. Size S - Head Circumference 19.0-20.5 inches Size M - Head Circumference 21.0-22.0 inches Size L - Head Circumference 22.5-23.0 inches Size XL - Head Circumference 23.5-24.0 inches