Function: 1. DURABLE MATERIAL: made of excellent aluminum alloy, surface oxidation treatment, durable, fine workmanship, high transmission accuracy, the closed timing belt is made of strong fiber-reinforced rubber, durable and flexible, has a long service life, giving you an unparalleled experience 2. ACCURATE AND STABLE: Provide accurate transmission. No slippage during operation, constant gear ratio 3. SUITABLE FOR DIY: ensure smooth transmission, accurate pitch, high transmission efficiency, good energy-saving effect, many DIY enthusiasts are praised for it, and will also be your best choice 4. SIMPLE STRUCTURE: Easy to install and remove with wrench, used together to make your 3D printer work more easily and conveniently 5. WIDE APPLICATION: As a stepper motor pulley kit, widely used in 3d printers, milling machines, gear grinding machines, drilling machines, CNC lathes, gear milling machines or other mechanical transmissions Specification: Item Type: Synchronous Wheel Material: aluminum alloy, rubber Timing Belt: Length: Approx. 200mm / 7.87in, Width: Approx. 6 mm / 0.24 inch Teeth: 20T and 60T Screw: M4 Package List: 4 x synchronous wheel 2 x Belt 1 x hex key