Wolfbike Unicase Bicycle Cycling PVC Helmet BMX MTB Off Road Safety Helmet Superlight Size: For head circumference (54-62cm) Unicase technology ,more safe and perfect Ventilation with 24 hole,use air cooling make the air free Anatomic design , senior double-sided velvet protection pad Material: Outside:PVC,inside:EPS,PU foam,nylon adjust belt, Impact protection