Features: High-precision thread ensures close connection with the bicycle hub and smooth operation. Variable speed positioning groove, uniform force, high lubrication, smooth operation and labor saving. Made of premium steel, which is strong and wear-resistant, not easy to rust, and has a long service time. Fine quenching and hardening, large-area hollow out to reduce weight, will not bring burden to riding. Easy to install and disassemble, it is suitable for folding bicycles or road bicycles.