Material: Carbon steel. Color: Silver. Use: Mainly for fixed gear bicycle hub fastening. Size: M9 M10 for option. Net weight: Approx. 16gram/PC. Package includes: 1xBolt. Features & Specs: Constructed by steel and chrome furnished, firm and durable in use; With anti-skid texture for firm fixing. Note: Normally, the front hub takes M9 and rear hub M10. But there are also some bicycle types taking M10 at both front and rear hub.