The coil spring does not move：the new patent designs a groove on the disc and cassette body to fix the spring, and the hub will not slip due to the displacement of the spring when it is engaged.
Improvement of waterproof seal：the new design places the waterproof rubber seal in the hub body which has good sealing performance and the oil in the cassette body is not easy to lose. V-type waterproof rubber seal reduce interference and resistance. Good sealing can also prevent the cassette form falling off.
