Size: Fit for 53~60cm head circumference Features: helmet body: ABS material, with good impact resistance and heat resistance, low temperature resistance, perseverance. Surface sandblast treatment, not reflective effect, particles, feel more. Characteristic two: helmet inner pad adopts high-density memory sponge. Ventilation net surface. Features: absorb external force, feel exquisite, soft and comfortable. In use, press the quick reset to protect the head effectively. It's different from a regular sponge. Commonly used sponge according to the structure is divided into high-density sponge, medium density sponge, low-density sponge three kinds. High density sponge, hole, very full, often used as sound-absorbing cotton, sofa cushion, soft decoration materials. Features three: BOA lacing sys.