1.[ MTB Helmet for Adults]: adult bike helmet is designed to fit head circumferences of 21.65 - 22.83 inch and 23.22 - 24 inch (MEDIUM SIZE: 21.65-22.83' / 55-58cm; LARGE SIZE: 23.22-24' / 59-61cm), ensuring a snug and secure fit, removable pads make this adult cycling helmet fit to different head size and fits both men and women. [ KIND REMINDER]: ALWAYS take a head measurement. Head sizes and shapes can vary, even within an age range. Using a helmet that doesn't fit can be dangerous! 2.[Safety Cycling Helmet]: This full face bike helmet is equipped with an EPP chin support, this adult mountain bike helmet enhanced conservation, thus making sure you are in a case of an accident. Complies with U.S. CPSC Safety Standard for Bicycle Helmets for Persons Age 5 and Older. 3.[ Design]: This adult mountain bike helmet are only 700g (24.69oz) and 720g (25.39oz) for medium and large size, ensures long-term use without causing any strain or discomfort to your head and neck. 4.[Premium Ventilation]: Designed with over 31 vents, this helmet provides ample airflow and cooling. This specialized ventilation design allows air go through the helmet which can help increase the speed and keep cool. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.