The MESA is the perfect trail riding helmet. Vertically anchored retention system for a secure and safe fit. Fully adjustable dial fit retention system provides a custom, comfortable fit with the turn of a dial. Removable cushioned head liner for easy care. Mesh covered vents keeps dirt and debris out while providing maximum air circulation. Western trim brow band. Fully adjustable nylon harness system with quick release snap buckle. Rubberized matte paint finish prevents scratches. Brown or Black. S/M --20 1/4"- 21 7/8" ( 6 1/2- 7); L/XL-- 21 7/8"- 23 1/2" ( 7 - 7 1/2) SEI approved to ASTM F-1163-04a.