A. Bicycle Rear Derailleur Hanger, Rear Derailleur Adapter, Bicycle Drivetrain Protection Frame, Bicycle Rear Derailleur Accessories B. 1. The hanger is an accessory of the frame (except for the claw - type rear derailleur) and has little relation with shifting and the rear derailleur. 2. Most hangers are made of 6061 aluminum alloy. One might wonder why steel is not used. 3. When accidentally crashing, one may hit the derailleur, causing it to deform and potentially affecting the drivetrain function. 4. The rear hanger is made of aluminum alloy, which allows a certain degree of deformation to protect the derailleur from damage. 5. In case of severe jolts, the rear hanger can break and then be replaced with a new one, thus reducing the frame's maintenance cost. 6. Steel is relatively too strong to provide protection. C. Specification Parameters: 1. It can be used to upgrade or replace the rear derailleur claw; it is relatively stronger and more durable to improve shifting performance. 2. It is precision - machined from solid 6061 aluminum via CNC with relatively precise tolerances. 3. It is stronger than some device hangers and can improve shifting performance. 4. It may break before the frame is damaged to fulfill its main function. 5. All hangers come with instructions and hardware. 6. It can be directly replaced on the device to ensure compatibility. 7. Model: A01 D. Mountain and Road Bicycle Rear Derailleur Protector Bracket Protect your rear derailleur from damage.