OutdoorMaster Youth & Kids Bike Helmet -Beetles Jr.Adjustable Multi-Sports Skateboard Helmet with Removable Liners for Balance Bike, Toddler Scooter Pink Flower Small: 46-52cm / 18.1"-20.5"

Durable: Built for both comfort and impact resistance with reinforced ABS shell & thickened shock-absorbing EPS core
Extra Removable Lining: Skateboard helmet with two removable liner for different head sizes and easy to wash the sweat away
A Helmet for Multi-sport: Smooth Ventilation System helps to protect and enjoy skating, cycling, BMX and etc. Complies with U.S. CPSC Safety Standard for Bicycle Helmets for Persons Age 5 and Older
Double Adjustment: Well-attached & long-lasting adjustment dial and skin-friendly adjustable chin strap maximize the best fit and comfortable wearing
How to Measure A Proper Helmet: To find the right size bike helmet, start by measuring your head circumference, wrap a flexible tape measure around the largest portion of your head about one inch above your eyebrows. Or wrap a string around your head, then measure the length of string with a yardstick. Size Large is recommended if your size is between 21.3-22.8 inch (54 cm-58 cm)