ABS outer shell for impact protection and soft EVA absorption liner. Ear protectors prevent ears from scratch and don%92t affect hearing.Removable ear protection pads is suitable for more usage needs. 11 vents system for breathing.Keep your head cool on hot days. Adjustable back of head dial.X-Large(23.6-24.4in)|(60-62cm).Large(21.7-24.0in)|(55-61cm). Medium (20.9-23.2in)|(53-59cm). Small(20.1-22.0in)|(51-56cm). Helmet weight:413g.Meets CE EN 1385 standard.