This twelve-speed gravel rear derailleur features a charge port, LED, function button and an EW-SD300 type port used to connect the derailleur to the battery.
Both the rear derailleur and the front derailleur connect to the battery using a wire. The shift levers send their shift commands to the rear derailleur wirelessly.
Since this is a gravel rear derailleur, it also has a clutch mechanism that can be switched on/off. When turned on, this mechanism will ensure proper chain retention and smooth shifting on rough terrain.
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Just like the 11-speed GRX rear derailleurs, this 12-speed RD-RX825 falls into the road category. This means that it's fully compatible with other 12-speed Di2 groupsets. If you want to build a 12-speed road bike with a clutch rear derailleur, you can!
What is a rear derailleur's total capacity, really? Why is there a top sprocket minimum? And what about front derailleurs? Chain line, total capacity, Top gear teeth? This page explains all of those, and more.
