Engineered for riding extremes, the Sierra's rugged covering not only looks good, but also withstands the toughest terrain on the trail. Its excellent ventilation and mesh covered vents have made this the trail rider's number one choice. The best selling western helmet sizes: S (up to 7), M (7 - 7 1/4), L (7 3/8 - 7 3/4) | Troxel Sierra Trail Helmet in Brown | Size Large