Features 1、Enlarging Flywheel Speed: Bicycle rear derailleur hanger amplifies the speed of the cassette for smoother changes, a great accessory for cyclists. 2、Improve Climbing Ability: Bike tail hook extension extender can relieve the spring tension of the rear derailleur and improve the climbing ability of the bike. 3、Aluminum Alloy Material: Bike rear derailleur hanger is made of aluminum alloy material, CNC precise machining, durable and easy to install. 4、Scope of Application: It can be increased by 41mm, and the tooth volume of 20 to 22 teeth can be increased. It is often used when the large teeth of the rear flywheel are changed to 36T 40T 42T 44T 46T 50T 52T 56T. 5、Good Workmanship: Professional manufacture, exquisite workmanship, beautiful appearance, stable performance, high reliability and long service life. Item Type: Flywheel Extension Tail Hook Material: Aluminum Alloy Weight: Approx. 19g / 0.7oz Specifications: As shown in the measured data, the screws equipped with the extender need to be installed with a 6mm wrench Application: Most tail hooks are compatible, but some tail hooks need to be modified by yourself! Package List 1 x Flywheel Extension Tail Hook 1 x Screw