Sram:

The SRAM RED Rear Derailleur has been designed to deliver the performance advantage you've come to expect from SRAM. With WiFLi, the rear derailleur lengthens its cage and gets a slight variation in geometry to accommodate an 11-32 cassette. The new range of gears is wider than the standard triple chainring system and saves well over 250 grams.

SRAM have paid rapt attention to the finer details, like adding a hollow titanium anchor bolt and even refining tooth geometry of the jockey wheel. The result is that the chain runs through the new RED Rear Derailleur smoother and quieter than ever before.