One Size, with included fitting pads for customized comfort and fit. This helmet is the GQ model of Shred Ready. With a 4-Point retention system that allows you to wear the helmet forwards or backwards. The armid fiber that is used makes a solid and practically indestructible helmet that is worth getting excited about. This is the kind of helmet to take on an adventure. Check out the Futaleufu River in Chile. Add this trip to your top 10!