Jeefree Color Gradient Adjustable Helmet For Multi-Sports Bicycle Scooter Inline ?Double Adjustment: Well-attached long-lasting adjustment dial and skin-friendly adjustable chin strap maxmize the best fit and comfortable wearing. ?Use for: This helmet could be used for many occasions such as bicycling, roller skating, skateboarding, hip-hop, rafting, head turning, river rafting, expansion, etc. ?How to use: Before you use the helmet, please untie the buttons that connect the straps on both sides of the helmet. Depending on the size of your head, rotate the red adjustable knob on the back of the helmet and attach the button in the middle of the strap ?Application: Designed for 5+ years old youth kids toddler, boys and girls, head Circumference is 48-54cm/19.7-21.2 inches , more than ten colors for your choice. ?Ventilation : Use of multiple vents, special aerodynamic design and breathable foam to reduce sweating and keep staying cool. It also reduces the high body temperature caused by intense body movements.