The heart of the Helios\\\'s extraordinary design and performance is Spherical Technology, which utilizes a ball-and-socket design powered by MIPS®, the market-leading brain protection system that can help to reduce rotational forces. Spherical Technology allows the helmet\\\'s outer liner to rotate around the inner liner during a crash, and also allows Progressive Layering of the inner and outer liners to provide more comprehensive protection and performance. In addition to advanced head protection, the Helios\\\'s 15 Wind Tunnel vents provide exceptional cooling power that\\\'s enhanced by our patented Roc Loc 5 Air fit system and plush, antimicrobial XT2 padding for exceptional sweat absorption. It\\\'s the ideal match for your road and gravel adventures. Key Features Spherical Technology\\\'s Ball-and-Socket design, powered by MIPS, helps redirect impact forces away from the brain by allowing the outer liner to rotate around the inner liner during a crash. Helmets with Progressive Layering feature a dual-density liner designed to address high and low-speed impacts, for more comprehensive energy management. The goal of Giro\\\'s Integrated MIPS®-equipped helmets is to reduce rotational forces, while enhancing fit and comfort by combining the MIPS® slip plane with the helmet\\\'s adjustable fit system. Giro believes that helmets equipped with this technology can reduce the amount of rotational force that may be transferred to rider\\\'s brain in certain impacts. Combined with the massive vents, internal channeling forces air to flow over the scalp, providing remarkable cooling power. This revolutionary fit system adds a new dimension to helmet performance by enhancing cooling, as well as fit comfort and stability. Using a patented design that suspends the helmet just slightly off the top of the skull, Roc Loc® 5 Air allows cool airflow to pass directly over your head, further enhancing the performance of vents and internal channeling that exhaust heat out of the helmet. Giro Helmet SizingSMLXLHead Circumference (CM)51-55cm55-59cm59-63cm61-65cm Helmets Buying Guide