SRAM SRAM Red Rear Derailleur - 2011 Black Edition

Material makes the difference: Exact Actuation™ combined with materials upgrades yields world-beating performance and weight savings.
Light weight, precision, and fluid performance put the new SRAM Red Rear Derailleur in a class of its own. Based on the already-superior design of the SRAM Force Rear Derailleur, the Red offering delivers even greater advantages thanks to a diet of structural carbon and titanium.
Hybrid ceramic bearing pulleys and the titanium parallelogram spring further supercharge the overall component speed, accuracy, and durability. Amazingly, these design choices yield an astonishing 153g mechanism.