Giro 2016 Women's Xara Mountain Cycling Helmet Construction: Full-wrap in-mold polycarbonateshell with EPS liner Fit System: Roc Loc 5 Vents: 17 Wind Tunnel vents with internal channeling Sizes: S 20-21.75in / 51 - 55cm, M 21.75-23.25 / 55 - 59cm