Developing cartridge including electrode to which adapter is detachably attachable

A developing cartridge comprising:

• a main portion comprising:
• a developing roller rotatable about a first axis extending in an axial direction of the developing roller;
• a casing configured to accommodate therein toner, the casing having an outer surface positioned at one end of the casing in the axial direction;
• an electrode electrically connected to the developing roller and positioned at the outer surface, the electrode extending in the axial direction;
• a gear rotatable about the electrode;
• and
• a protrusion protruding in the axial direction and rotatable together with the gear;
• and
• an adapter having an electric conductivity and detachably attachable to the electrode, the adapter being electrically connected to the electrode in a state where the adapter is attached to the electrode,
• wherein a total length of the electrode and the adapter in the axial direction in the state where the adapter is attached to the electrode is greater than a length in the axial direction of the electrode in a state where the adapter is detached from the electrode;
• and
• wherein the adapter is detached from the electrode to attach the main portion to a first type of image forming apparatus, and the adapter is attached to the electrode to attach the main portion to a second type of image forming apparatus.