This is a bicycle helmet. The main material appears to be expanded polystyrene. It's quite light. It has never been used, so there are no sweat stains, etc. It's the type that allows you to adjust the size with a dial. The following is a description from Mercari: Bicycle helmet with breathable pads and aerodynamic design. - Color: Carbon-like - Accessories: Visor - Interior: Breathable pads - Design: Aerodynamic design - Size adjustment: Adjustable straps Thank you for viewing. #Roadbike #Pistbike #Sportscycle