Gravel cycling is a bit of an enigma. While it's mostly new to the scene, it manages to evoke nostalgic feelings that we don't really get from modern road cycling these days. Between wool jerseys, steel frames with drop bars, and a sense of adventure that doesn't stop when the tarmac ends, it manages to captivate us with an undeniable vintage aesthetic. With that said, it's not all about throwing new technology to the side, and Shimano proves it with the GRX RD-RX817 Di2 Rear Derailleur that brings electronic shifting to the gravel scene, built tough enough for life off road, but with silent, uninterrupted shifts that are precise and reliable regardless of the terrain ahead. Like you'll find through the rest of Shimano's GRX rear-derailleur line, the RX817 comes equipped with borrowed technology from the mountain bike world with Shadow clutch mechanism that adjusts chain tension to reduce dropped chains and keep your ride quiet through the rubble. 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. The RX817 model comes ready to roll with a medium cage length, which accommodates both Shimano's 11-40t and 11-42t cassettes, 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 agains...