Feature: 1. Expanding the flywheel speed yet changes more smoothly, a great accessory for cyclists. 2. Can relieve the spring tension of the rear derailleur to enhance the bicycles climbing ability. 3. Professional manufacturing for stable performance and high reliability, has long service life. 4. Suitable for 8‑speed, 9‑speed, 10‑speed, 11‑speed, 12‑speed large flywheel tooth upgrade. 5. Made of high quality aluminium alloy, CNC accuracy machining, strong and durable, easy to install. Specification: Item Type: Rear Derailleur Hanger Extension Material: Aluminium Alloy Screw Material: Aluminium Alloy Process: CNC accuracy machining, aluminum alloy anodizing surface Size: Approx. 4.5cm/1.8in ID: Approx. 1.6cm/0.6in Fitment: For the 8-speed, 9-speed, 10-speed, 11-speed, 12-speed large flywheel tooth upgrade Package List: 1 x Rear Derailleur Hanger Extension 1 x Screw Note: Please slight 0‑2 cm error due to manual measurement. Thanks for your understanding.