Bicycle rear derailleur

A bicycle rear derailleur comprising:

• a base member having a first portion and a second portion, the first portion of the base member being mountable to a bicycle frame and the second portion of the base member being attached to the first portion of the base member and including at least a portion of a power supply attachment;
• a movable member movably coupled to the first portion of the base member and electrically connected to the second portion of the base member;
• and
• a chain guide assembly rotatably connected to the movable member,
• wherein the first portion of the base member is made of a first material, and the second portion of the base member is made of a second material, the second material being different than the first material, and wherein the second portion of the base member has a first side and a second side, the second side includes a recess at least partially defined by at least one protrusion made of the second material extending away from a surface at the second side of the second portion of the base member within which a power supply is positionable,
• the protrusion is defined by a first lateral side wall having a first base and a first tip, a second lateral side wall having a second base and a second tip, and a lip connecting the first base and the second base at a bottom of the second side of the second portion,
• the first tip located vertically above the first base,
• the second tip located vertically above the second base,
• wherein the first tip and the second tip extend a first distance away from the surface at the second side of the second portion of the base member, and the first base and the second base extend a second distance away from the surface at the second side of the second portion of the base member, the second distance being greater than the first distance.