DOT Safety Standard: motorcycle helmet: disassembled in the lining to k1.5 lbs) Type: Motorcycle Helmet Helmet Size: S (47-48CM), M (49-50CM), L (51-52CM), XL (53-54CM) (Accurately measure the head circumference and select size to avoid too much or too small). Scope of application: unisex Applicable scenario: motorcycle / ATV / off-road / endurance Helmet size tips (1) Wrapped tape measure more than half eyebrows one inch (2) Take two to three times the measurement results, choose the largest one.