YOUTH HELMET SIZES HELMET SIZE CIRCUMFERENCE (CM) CIRCUMFERENCE (INCHES) YS 49-50 CM 19.15"-19.50" YM 51-52 CM 20.10"-20.45" YL 53-54 CM 20.87"-21.26" ADULT HELMET SIZES HELMET SIZE HAT SIZE (INCHES) CIRCUMFERENCE (CM) CIRCUMFERENCE (INCHES) XXS 6 3/8"-6 1/2" 51-52 CM 20-1/8"-20-1/2" XS 6-5/8"-6-3/4" 53-54 CM 20-7/8"-21-1/4" S 6-7/8"-7" 55-56 CM 21-5/8"-22" M 7-1/8"-7-1/4" 57-58 CM 22-1/2"-22-7/8" L 7-3/8"-7-1/2" 59-60 CM 23-1/4"-23-5/8" XL 7-5/8"-7-3/4" 61-62 CM 24"-24-3/8" 2X 7-7/8"-8" 63-64 CM 24-3/4"-25-1/2" 3X 8-1/8'-8-1/4" 65-66 CM 25-5/8"-26" 4X 8-3/8"-8-1/2" 67-68 CM 26-3/8"-26-3/4" 5X 8-5/8"-8-3/4" 69-70 CM 27-1/8"-27-1/2"