Specification: Size: 55-61CM Weight: about 280g Material: PC+EPS+Insect mesh+adjustable brim Air holes:22 Inner width:17.5cm Structure: outer strong in-mold PC shell to against the shock and inner EPS can absorb the shock well. Product feature: 1 Compatible for road bike,for man and women. 2 It passed CE EN1078 Certification 3.it past the safety test 4.the EPS foam was thickened. Advantages:It has the good ventilate function with air holes,and good protective performance cause it was specially designed for the endurance racing athlete.The inner EPS shock-release system was put in.and we used the aramid filament to enhance the strength.