The GRX Di2 12-speed rear derailleur from Shimano incorporates a wireless connectivity unit and charging port within its design, guaranteeing swift and dependable gear changes for mixed-terrain adventures while facilitating effortless recharging. Equipped with Shadow RD+ technology, it effectively minimizes chain slap and maintains accurate shifting across rough terrain. With its convenient built-in ON/OFF switch, wheel removal becomes a hassle-free task. Compatible with 11-34T and 11-36T 12-speed cassettes, the RD-RX825 supports both Full and Semi-Synchronized shift modes, offering riders enhanced customization options to suit their preferences.