This helical gear can be used for 90 degrees of transmission. it has good wear-resistance,low niose,transmission smooth and steady. Feature: good wear-resistance low niose transmission smooth and steady. Material:Cu+engineering plastics Specification： Gear A: tooth number(Z):15, Outer diameter:18.6mm, Thickness:6mm, Inner diameter:6mm Gear A: tooth number(Z):10, Outer diameter:12.8mm, Thickness:6mm, Inner diameter:4mm For any technical support or suggestion, please kindly go to our forum.