A. This mountain bike rear derailleur converter, also known as a bicycle frame hanger, is designed for mountain bikes and can effectively expand the functions of the frame. It is made of aluminum. This material is not only lightweight, reducing unnecessary weight for the whole bike and making cycling easier, but also has good durability and corrosion resistance. It can adapt to various complex cycling environments and is not easily damaged even after long - term use. B. The converter features an extended seat design that can effectively extend the flywheel. Using it can optimize the bike's transmission system and improve the accuracy and smoothness of shifting. This allows cyclists to quickly and accurately complete shifting operations on different road conditions and enjoy a smoother cycling experience. C. In terms of specifications, its model is L23A, which has good adaptability and can be perfectly matched with various types of mountain bike frames. Cyclists from different regions such as Africa, Europe, South America, Southeast Asia, North America, Northeast Asia, or the Middle East can use this frame hanger to enhance the performance of their mountain bikes.