Shell made of ABS for light weight. BOLT'™ system - ensure compatibility among a large range of accessories with an easy and intuitive attachment system. Extremely comfortable and easy to adjust wheel ratchet adjustment system. 6 points suspension for more comfort. Changeable and comfortable sweatband. Size: 52 - 68 cm. Certified as per EN 397:2012 with optional requirement for Multi Metal, extreme temperatures - 30°C, Lateral Deformation, and Electrical insulation 440 V a.c. (electrical insulation 44OV under EN397 just on the unvented version). Certified as per EN 50365:2002 Electrical class 0 for installations with nominal voltage up to 100OV A.C. and 1500V D.C. in vented and unvented version.