The pulleys are produced by high-precision automatic lathe machining, with machining error within 0.005mm. Advantages: Smooth motion, high printing precision, low noise, can greatly improve the printing speed. Perfect For 3D Printers: for CR-10, CR-10S, Tevo Tarantula, CNC router hybrid, 8020 3030 and so on. With Bearings: Yes Please Kindly Note: the pulley has of many kinds size,please confirm correctly before you bought. Outside Diameter: 0.94inch/23.89mm Inner Diameter: 0.62inch/16mm Bore: 0.19inch/5mm Thickness: 0.4inch/10.23mm Size: 24*6*5mm Color: Black Material: steel + rubber Package Contents: 12 * 625zz POM Wheel Only the above package content, other products are not included. Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.