Product Details:

SAFETY: Adult bike helmet is made of Multi-Density EPS and high toughness PC shell with Integral Moulding Technology. Also helmet has the CPSC certificated.
Weight: M (About 260g), L (About 278g) Size: M (55-58cm), L (58-61cm)

Measurement Method
Use a soft ruler to make a week around A and B. （Hair is also counted） And then you can purchase the helmet according to your needs.

PC + One Hemming

Reduce windage

Breatable

Adjustable head circumference

360° Rotatable

Magnetic-snap

Easy to wear and take off

EXCELLENT HEAT DISSIPATION: Comfortable temperature from excellent heat dissipation. Total 25 vents on helmet, no matter on a cycling race or a hot day, this road bike can aspirate more cool air to keeping the comfortable temperature, give you a enjoyable cycling experience.
SAFETY: Adult bike helmet is made of Multi-Density EPS and high toughness PC shell with Integral Moulding Technology. Also helmet has the CPSC certificated.
ADJUSTMENT SYSTEM: The latest magnetically helmet fastener, side strap adjust button and size adjust dial make up the easy-use adjustment system, which is good for the bike helmet adjust to different head size and more suitable for both men and women. ( M: 21.2 - 23.2 inches (54-59cm) L: 22.8 - 24.8 inches (58-63cm))
COMFORTABLE & DETACHABLE PAD: Detachable and washable anti-microbial pad design for increased comfort and absorb sweat. Also you don't need worry about pad getting wet, good gas permeability can keep your mens bike helmet clean and no peculiar smell.