Material:Aluminum Alloy.The surface is oxidation finished.It makes the material to be more antirust,corrosion resistant,wear resistant and durable. Advantages:Stable performance and high efficiency. Low friction, low noise a nd high accuracy. Application:3D printer,CNC machine,drilling machine,milling machine, and other transmission machine. Teeth:30/Bore Diameter:8mm/Belt Width:6mm Package:8 pieces (Come with wrench) GT2 Timing Belt Pulle.Low friction, low noise a nd high accuracy.