Cool and Comfortable: 12 air vent can reduce sweating keep head cool. removable comfy liner and adjustable chin strap with side release buckle comfortable and secure. Adjustable Size: 2 sets of inner pads with different thickness(8mm/10mm) for different head circumferences. The bike Helmet come with adjustable regulator and strap which make it flexible to fit the size of kids children adults. Size Small(20-21.7 inch) suitable for 2-5 years old; Size Medium(20 - 22.8 inch) suitable for 5-16 years old; Size Large ( 23-24 inch) suitable for adults. Please according to head circumference weight and age choose. Manufacturered by Kuulla. Wide Use and Perfect Gift: The safety bike helmet is suitable for outdoor cycling bicycling skateboarding roller-skating ice-skating riding self balance scooter etc. Its a great gift for birthday Christmas Thanksgiving Halloween and other festivals. 100% Customer Service Satisfaction: Any questions please feel free to contact us we would deal with it in a 24 hour time. and we provide a 100% guarantee with 24 months warranty. Impact Resistance: CPSC certificated helmet is made of tough and durable ABS shell and shock-absorbing EPS core which would help absorb the impact and protect the head during impact.