Sourcing a Di2 groupset piecemeal is a game of matching part numbers across battery types, wire lengths, cassette compatibility, and lever generations—and getting one wrong means a return shipment before you've turned a wrench. Shimano's GRX-RX825 Di2 2x12-Speed Kit sidesteps that by bundling the electronic shifting and hydraulic braking pieces into a single box, leaving only the frame-specific parts—crankset, bottom bracket, rotors, and the Di2 wires that route through your specific frame—for you to spec separately. This particular kit configuration ships with the 11-36T cassette option, which is the wider of the two officially compatible cassettes for the RD-RX825 rear derailleur.

The RX825 shifters communicate wirelessly with the derailleurs and are powered by CR1632 coin cell batteries rated for roughly 3.5 to 4 years of use. There are no cables running from the levers down through the bar tape and into the frame, which cleans up cockpit routing on bikes with integrated handlebar setups. From the battery back to the derailleurs, Shimano runs small-diameter EW-SD300 wires directly—no junction boxes—but those wires are sold separately since length depends on frame routing. The BT-DN300 internal battery lives in the seatpost and supplies both derailleurs from one central source.

The RD-RX825 rear derailleur uses Shimano's Shadow RD+ clutch to keep chain slap under control on chunder, and the built-in on/off switch makes wheel removal painless. It handles 11-34T and 11-36T 12-speed cassettes, with 36T being the hard ceiling. The FD-RX825 front derailleur is braze-on mount and is tuned specifically for the RX820 (48/31T) and RX610 (46/30T) 2x cranksets—both of which you'll source separately. Full and Semi-Synchronized shift modes are available through the E-TUBE PROJECT Cyclist app, along with button remapping across the three Di2 buttons per lever.... Read More