A. This bicycle derailleur hanger adapter is made of aluminum alloy, offering good durability and stability to provide reliable support for your cycling experience. B. It comes in two specifications: the long version L41 and the short version L23. Different specifications can meet different usage needs. Whether it's a road bike or a mountain bike, you can find a suitable adapter. The hanger hook of the long version L41 extends longer, providing more expansion space for the bicycle, which is suitable for cycling enthusiasts with high requirements for frame space. The short version L23 is more compact and can meet the needs of users who don't have high space requirements but need precise adaptation. C. This derailleur hanger adapter can serve as an extension seat for mountain bikes and is also compatible with rear derailleurs and cassettes, effectively improving the performance of the bicycle. It can make the operation of the rear derailleur smoother and the gear shifting more precise, allowing you to easily handle various road conditions during your ride. D. Whether you're speeding on a flat road or traversing rough mountains, this bicycle derailleur hanger adapter will be a good companion for your cycling, adding more functionality and practicality to your bicycle.