The 100% Aircraft Composite Helmet boasts a precision engineered fibreglass composite shell that makes this DH helmet so lightweight, not forgetting how strong that fibreglass construction makes the Aircraft Composite. Ventilation is the stand-out feature on the Aircraft Composite with their enhanced Active Cooling System that manages and channels airflow to create one of the most venilated DH helmets on the market. Designed with 25 mesh vents across the chinbar, forehead, top and back to get maximum airflow in and out towards the back ventilating the entire helmet to keep you cool and comfortable. The cheek pads and chin strap comfort liners are anti-microbial and washable, they feel comfortable against skin and can be chucked in the wash after a heavy day to keep them fresh. The Aircraft Composite Helmet features an integrated compartment accepting inflatable emergency release systems and emergency release cheek pads that can be quickly and safely removed if required. It's also compatible with most popular neck brace systems. Sizing: Medium: 57-58cm (Cheek pad 25mm, Liner 10mm) Large: 59-60cm (Cheek pad 30mm, Liner 14mm)