The Tracer Helmet by Black Diamond is a comfortable shield from falling rock and ice. Features in-molded EPS in a polycarbonate shell - mesh-covered vents and three sizes - each with a quick-adjust system for a secure fit.Features: Small: 49-57 cm (19.3-22.5 in) Medium: 56-60 cm (22-23.5 in) Large: 59-63 cm (23-25 in)