3 sizes available. Small: 18.9"-21.3" (48-54 cm), suitable for kids 2-8 years old. Medium: 21.3"-22.4" (54-57 cm), suitable for youth 8-14 years old. Large: 22.4"-24" (57-61 cm), suitable for people aged above 14 ABS shell resists impact and high quality EPS foam provides shock-absorbing....