This genuine Shimano replacement part is the exact magnetic charging port cover that comes with your Di2 R9250 Rear Derailleur. Designed for easy replacement, it ensures that if the original cover gets damaged or lost, you can easily swap it out. The cover helps protect the magnetic interface from dirt and debris while providing some added defense against water intrusion. Since this interface serves as your charging point and houses critical Di2 electronics, keeping it covered is essential for optimal performance.