Features: Experience perfect gear transitions with our Rear Derailleur Converter that enables you to shifts more smoothly, easily adjust the tightness, and ensure precisions.Make of strong aluminum Alloys, light weight, corrosion resistant, strong and Enduring.The bicycles rear derailleur is used to extend the rear derailleur, suitable for mountain flywheel 40-50T road flywheel.Easy to install: It is simple to replace and install the hanger, and adjust the tension and speed more smoothly.The bike rear derailleur make the flywheel speed change more smoothly.Specifications: Materials: Aluminum AlloysColor: Black/Redness/Blue/Metal Color/GoldSize: about 4.5x2cm/1.77x0.79inchPackage Includes: 1Pc Bicycles Rear Derailleur Hanger Extensionnote: Please allow 1-2cm errors due to manual measurement, make surely that you not mind before order. Due to difference between different monitors, the picture may not reflect the actual color.