Gravel riding has been taken to new levels in the past years. What used to be a niche cycling event for the rebels and rule breakers has taken to the masses, with events that are packed with faces from all walks of cycling life, from the avid endurance athlete to the roadie, and everything in between. And with such growth, it doesn't surprise us at all that Shimano made its debut into the gravel scene recently with its launch of a gravel-specific groupset. Now, bringing things even further into the future, Shimano offers its GRX group with a little bit of Di2 magic dusted on top, and the GRX RD-RX815 Di2 Rear Derailleur is ready to hold things down in the rear end. The GRX Di2 rear derailleur takes the shape and tech that we love from the standard GRX rear derailleur, like the clutch mechanism that secures your chain on rough roads, and ads in electronics for crisper shifting than before. Following in the footsteps of the revamped Dura-Ace and Ultegra groups, this GRX derailleur gets its Shadow cage treatment placing it closer to the frame and under the cassette keeping it out of harm's way and less likely to take the brunt of a driveside crash. This also allows the derailleur to move in a much more linear path allowing for shorter throws with less effort. T RX815 model comes in one cage length, short, which accommodates an 11-34t cassette allowing for a wide range gear ratio when paired with a double without the usual huge jumps between the cogs like on a 1x setup. Sticking to what the brand's customers know well, Shimano continues to use the Dura-Ace, Ultegra, and Tiagra designation with the GRX line, with this particular model falling under the Ultegra umbrella, which means it gets the usual materials and finishes that we expect from a groupset that's just one step from the top. Its weight, smoothness, and durability make it more than capable of racing against the competition on course, or the sun to your campsite for the night on a bikepacking trip.