The Record Mid-Cage rear derailleur is specifically built to accommodate a double drivetrain using a 13/29 rear cassette, as well as triple drivetrains that use any cassette ratio except for 13/29. Like the short cage version, the Mid-Cage features a carbon fiber pulley cage. It's interesting to note that the Mid-Cage rear derailleur is built with multidirectional carbon fiber. The stresses generated by the longer cage of the Mid-Cage are best withstood by carbon fiber distributed multidirectionally along the entire length of the component. Like the Short Cage version, though, the pivot and hangar bolt here are both made from titanium, and the pulleys have been redesigned to increase the quietness of the drivetrain. 193g.