Shimano GRX DI2 RD RX825 12 Speed Rear Derailleur Brand_ZENO Frames 1x12 speed Ride faster energy that Frames 1x12 speed 28T steel ring 11T Fluoric coated link bushings 4 Pulley Guide pulley bearing Sealed bearing Pulley Tension pulley bearing Sealed bearing Pulley Teeth 11 13T Pulley Sunken type pulley screw ✔ B axle Hollow axle ✔ B axle 2 Hollow axle ✔ Di2 connectivity wired Di2 shifting ✔ Di2 connectivity wireless Di2 shifting ✔ Di2 connectivity wireless Bluetooth® LE custom (*1) Adjust mode information ✔ Di2 connectivity wireless Bluetooth® LE custom (*1) Di2 battery level ✔ Di2 connectivity wireless Bluetooth® LE custom (*1) Gear position ✔ Di2 connectivity wireless Bluetooth® LE custom (*1) SHIMANO STEPS data items (*3) ✔ Di2 connectivity wireless Bluetooth® LE custom (*1) Compatible with E TUBE RIDE ✔ Di2 connectivity wireless Bluetooth® LE custom (*1) Compatible with E TUBE PROJECT ✔ Di2 connectivity wireless ANT private (*2) Adjust mode information ✔ Di2 connectivity wireless ANT private (*2) Di2 battery level ✔ Di2 connectivity wireless ANT private (*2) Gear position ✔ Di2 connectivity wireless ANT private (*2) SHIMANO STEPS data items (*3) ✔ Firmware update by E TUBE PROJECT ✔ SD50 port (pcs) 0 SD300 port (pcs) 1 SD50 connector (pcs) 0 SD300 connector (pcs) 0 LED for system status ✔ Charging cable EW EC300 Gravel tuned clutch tension Switch stabilizer ON OFF to match terrain: ON for gravel