Path Discovery Outdoor Cycling Bike Helmets Material:EPS,ultralight anti-shock composite material shell Size:about 10.6*8.3*4.9in/27*21*12.5cm,weight:approx 225g/0.5lb Head circumference:suitable for 52-62 cm/20.5-24.4 in 18-hole design is not only unique and beautiful,fashion models,and hole design is very reasonable,reduce resistance,confortable,breathable,easy to wear. Rortary adjust design,more convenient to adjust the tightness of the helmet.