Features:1.Every product has a unique Manufacturing Part Number label on the inner package that proves it has been qualified,which include Part Number,Model Number and inspection date information;2.If you have any questions about the item,please provide us the Manufacturing Part Number for checking,your profits will be guaranteed.3.Made of brass, long time service.4.0.5 modulus , 20T worm wheel, 5mm bore worm gear shaft5.Worm Shaft Z1=1, turn a round of worm gear T, can get a large transmission ratio, generally in the power transmission, the transmission ratio I=10-80, like big transmission ratio, if use with gear transmission, will need to take the multi-stage transmission.Specifications:Material: BrassColor: YellowModulus: 0.5Weight:15gSize of worm wheel:T:20T Dia:11.2MMHeight:12MM/0.47 InchOuter Diameter:11MM/0.43 InchHole Diameter:4MM/0.16 InchStep Size:9x7MM/0.35x0.27 Inch ( Dia x H)Overall Size:12x11x4MM/0.47x0.39x0.12 Inch( H x OD x ID)Size of worm gear shaft:Height:20MM/0.79 InchOuter Diameter:9.7MM/0.38 InchInner Diameter:5MM/0.2 InchSize:20x9.7x5MM/0.79x0.38x0.2 Inch( H x OD x ID)Package include:1 x worm wheel1 x worm gear shaft2 x screws