Rowan has you covered when the mountains get steep and the trails get tricky. Moisture-wicking interior pads and 14 vents keep things from getting too sweaty, and the easily adjustable straps and ErgoKnob dial ensure a perfect fit every time you ride. Features: Bike helmet designed for mountain biking 14 air vents and a contoured design for optimal airflow Easy-to-adjust nylon straps and an ErgoKnob dial for a snug fit Removable visor shields the sun and provides better visibility Interior padding wicks away sweat and is removable for easy cleaning Complies with the U.S. CPSC Safety Standard for Bicycle Helmets for Persons older than Age 5 One Size: 21.25-24 in.