WJ series worm-gear speed reducer is new, the appearance is beautiful, small, heavy to output moment, has steady transmission, and has little noise. Can unite with electrical machinery or a stepless derailleur of awl of UD series planet directly, the structure is compact. Worm gear output for hole, user mix incline and exert oneself axle only, too can mix pair incline and exert oneself axle, there is greater flexibility.