Description: (from giro.com) The Xen balances the smooth, low profile style and coverge of skate-style helmets with the lighter weight and ventilation of high-performance XC helmets. It's the enlightened choice for today's all-mountain ride style. Fit System: Roc Loc 4. Construction: In-mold Hardbody. Ventilation: 17 Wind Tunnel vents, internal channeling. Features: P.O.V. adjustable visor. Weight: 11 oz. / 310g. Sizes: Small (51-55cm), Medium (55-59cm), & Large (59-63cm).