Impact is EverythingThe Aether MIPS combines airy, open design with a revolution in rotational energy management to advance head protection for cyclists. Inside the Aether, a dual-density EPS foam liner helps to manage a wide range of impact energies, while also boasting deep internal channeling to provide cooling airflow. Our proprietary MIPS Spherical technology is integrated between the layers of EPS foam instead of against the riders head giving riders the benefits of MIPS without any obstruction to comfort or cooling power. Outside, a sleek 6-piece shell forms a stunning silhouette around the massive vents, which get added structural reinforcement via a shatter-resistant AURA reinforcing arch. The final touch is our Roc Loc 5+ Air fit system, featuring 3-way fit tuning, that allows easy adjustment in seconds for the ultimate in comfort. Features: MIPS Spherical Technology, Independent liners with spherical interface, Roc Loc 5+ Air fit system, AURA reinforcing arch, Nanobead EPS foam, Eyeglass grippers, CoolFit anti-microbial padding Construction, Independent liners with spherical interface, In-Mold construction with EPS liner and progressive layering, Six-piece polycarbonate Hardbody Fit System, Roc Loc 5+ Air MIPS Ventilation, Wind Tunnel vents with internal channeling Sizes: S 20" - 21.75" / 51cm - 55cm M 21.75" - 23.25" / 55cm - 59cm L 23.25" - 24.75" / 59cm - 63cm Certification: CPSC Bicycle - Complies with the US CPSC Safety Standard for Bicycle Helmet for Persons Age 5 and Older.