Ultegra RX, GS 11 Spd. Di2With an integrated chain stabilizer mechanism, the ULTEGRA RX 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. The RD RX805 DI2 version offers the digital precision of SHIMANO electronic shifting and synchronized shifting. CAGE LENGTH: GS Medium TOTAL CAPACITY: 39T MAX FRONT DIFFERENCE: 16 AVERAGE WEIGHT: 280g