... Alloys 3.Type:Trapezoid tooth,T synchronization ,HTD(STD)synchronization Timing Belt Pully Specification:Trapezoid tooth MXL,XL,L,H,XH,XXH ... work without sliding 3.It's stable, low noise 4.High transmission efficiency, save energy obviously 5.No pollution, can work ... If you need more information,welcome to contact us. Standard Timing Belt Pully