Features: 20 Teeth Timing Pulley providing a smoother transition between belt, good performance for 3D printers GT2 timing belt pulley system especially suited for linear movement and positioning. Contact with the 20 tooth side which minimizes the risk of the belt slipping. Package Included: 2pcs x 2GT 20T Bore 8mm Double-Headed Timing Pulley Warm Notices: 1.We guarantee your 100% satisfaction! If within 90 days you are not 100% satisfied return your product for a full refund! 2.We are always welcome to our friendly customer support team for any product issue at our Amazon store. We provide e-mail reply within 24 hours to afford you the fullest satisfaction. LIFETIME GUARANTEE -BTMB offers the best customer service in the industry. For any reason you decide that our product is not for you, send 1 simple email and receive a 100% money-back refund, no questions asked (No need to return the product)