Package Included: 1*helmet Description: Brand: RNOX Suitable for: road bikes, mountain bikes Technology: One-piece helmet Color: white, black, red, silver, fluorescent green, gradient blue, gradient purple Size: 55-62, head circumference 56-62cm/ 21.65"- 23.62", head width 17.5cm/ 6.88", there is an adjusting knob to adjust the head circumference size. Helmet size: 27*21*14 CM Weight: 210g Vent: 21 Material: shell imported PC + imported EPS material Shell structure: In-mold polycarbonate shell with EPS lining Inner shell: thermoforming to enhance shock absorption Structure: External IN-MOLD (integrated molding) impact resistant PC, internal EPS integrated molding to absorb impact technology Specifications: Comprehensive performance and protection: RNOX's helmet test laboratory design