Features: 13 pieces of passive round pulley for CR-10 series (CR-10/CR-10mini/CR-10S/CR-10S4/CR-10S5) and Ender-3 3D printers. Inner diameter: 6mm/ 0.2 inch, outside diameter: 25mm/ 0.98 inch. Made of high-quality material, rust resistant and wear resistant. Fine workmanship and high-precision within 0.005mm error. Smooth motion and low noise, excellent friction resistance and operate smoothly.