Bicycle rear derailleur

A bicycle rear derailleur comprising:

• a chain guide including a first guide plate, a second guide plate and a guide pulley, the guide pulley being rotatably disposed between the first and second guide plates;
• and
• an indicator marked on at least one of the first and second guide plates such that the indicator is disposed on or in an outer periphery of the chain guide,
• when the bicycle rear derailleur is mounted to a bicycle, the indicator being indicative of a setting position of an outer circumference of a sprocket of a bicycle rear sprocket assembly relative to the guide pulley.