description of goods: This synchronous aluminum belt pulley is designed for 3D printer. It is an 3D printer accessory for 6mm wide belt with 20 teeth. As an synchronous pulley wheel, you will find it perfect for 3D printer or similar projects. Feature: Adopt high quality aluminum alloy, excellently machined, finished smoothly. This pulley is for 6mm width 2GT timing belt. 2pcs M3 keyhole placed in 90 degree angle. Each of the two sides of the wheels were mounted bearings. Perfect choice for building a 3D printer or similar projects. Specifications: Material: Aluminum Alloy Height: 16mm / 0.629 Outer Diameter: 16mm / 0.629 Inner Diameter: 5mm / 0.196 Belt Width: 6mm / 0.236 Quantity: 2 Weight: 13g(approx.) Package Includes:2 x Belt Pulleys Note:1. Please allow 1-3mm error due to manual measurement. Thanks for your understanding.2. Monitors are not calibrated same, item color displayed in photos may be showing slightly different from the real object. Please take the real one as standard.