Rear derailleur with one-piece chain cage

A rear derailleur assembly for mounting to a bicycle, wherein the bicycle includes a frame, comprising:

• an upper body portion configured to operationally engage the rear derailleur assembly to the frame;
• a controller portion pivotally connected to the upper body;
• a lower body portion pivotally connected to the upper body and pivotally connected to the controller portion;
• and
• a chain cage assembly;
• wherein the chain cage assembly includes at least two pulleys configured to engage a chain of the bicycle, and a one-piece chain cage configured to retain each pulley at a particular fixed position;
• wherein each pulley is rotatable relative to the one-piece chain cage at the particular fixed position of the pulley;
• and
• wherein the lower body portion is operationally connected to the one-piece chain cage and configured to allow the one-piece chain cage to pivot relative to the lower body portion;
• and wherein the one-piece chain cage includes at least one hollow.