The Petzl Elios helmet has a high density expanded polypropylene foam headpiece on the inside and a thermoformed ABS outer shell, providing both lightness and strength. The ergonomic shape provides maximum protection while ensuring a clear field of vision. A single adjustment wheel in the back and an adjustable chinstrap allow for efficient and quick adjustments. Four exterior hooks and a groove in the outer shell are designed to attach and secure a headlamp. Nothing has been left out in this simple, but refined helmet. Specs: Sizing: Size 2 (dia: 53-61 cm) Weight: Size 2 (330 g)