uxcell Aluminum MXL 15 Teeth 4mm Bore Timing Belt Pulley Synchronous Wheel for 6mm Belt 3D Printer CNC Material: Aluminum; Durable and virtually. Teeth: 15; Bore: 4mm; Suits to the timing belt which is 6mm width. Used widely in milling machine, CNC engine lathe, gear shaper, hobbing machine, drilling machine or other machinery transmission occassions. Package Content: 1 X MXL 4mm Bore Timing Pulley