Scorpion EXO-R420 GraphiteThe EXO R420 redefines what you can expect in a sub $200 full face helmet with state of the art materials, performance features, sleek modern design, refined fit, and a dual safety homologation. A combination more commonly associated with helmets at twice and even 3 times the price! HELMET SIZING CHART SIZE INCHES CM HAT SIZE Small 21 5 8 22 55 56 6 7 8 7 Medium 22 7 16 22 3 4 57 58 7 1 8 7 1 4 Large 23 1 8 23 5 8 59 60 7 3 8 7 1 2 X Large 24 24 3 8