With an integrated chain stabilizer mechanism, the Shimano GRX derailleur provides a quieter experience and shifting security and precision on mixed terrain. For rides on smooth surfaces, the derailleur features and ON/OFF switch for the chain tensioner. Features Adjustable chain stabilizer prevents chain slapping and drops. Switch stabilizer ON/OFF to match the terrain. Gravel-tuned clutch tension. Compatible with current road Dual levers. Low sprocket: Max. 34T/Min. 30T. Total capacity: 40T. Smooth and reliable mixed surface shifting.