Timing belt: The timing belt is made of premium rubber, and flexible. It's designed specifically for linear motion, high positioning accuracy. Round tooth profile guarantees that the belt tooth fits smoothly. Pulley: It's used together with timing belt, very convenient to use. 20 Teeth contact with the belt, that minimizes the chance of the belt slipping. Locking Spring: With the springs, you can add the right tension you need and make your prints much more precise. Mounting Block: The mounting block is used in open belt buckles for 2GT belt (and some other models). Make sure that the is firm and free from loosening. Compatibility: compatible with most 3D printers. Attention: Small parts, keep away from children! Timing Belt: Type: Material: Rubber Shape: Open timing belt Length: 5m Width: 6mm Pitch: 2mm Pulley: Teeth: 20 Total width: 16mm Diameter of bore: 5mm Groove width: 7mm Flange: Dual Material: Aluminium Idler: Teeth: 20 Diameter of bore: 5mm Total width: 8.5mm Material: Aluminium Timing Belt Tensioner Spring: Material: Stainless steel Color: Silver Inner Diameter: 5mm Wire Diameter: 0.8mm Circle number: 7 Suitable for 6mm timing belt Easily added the right amount of tension to the belt Mounting block: Material: Aluminum Teeth width: 0.85mm Teeth depth: 0.9mm Pitch: 1.1mm (the groove part) Size: 9 x 40mm, the middle hole is mounting hole. colour:black Material:Aluminum + rubber Package Contents: 1 * 5M Timing Belt 4 * Pulley 4 * Idler wheel 4 * Tension Spring 8 * Screws 2 * Mounting block 1 * Hex Wrench Only the above package content, other products are not included. Note: Light 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.