Abstract: An example image forming apparatus includes a frame, a first shaft supported by the frame, and a first coupler. The first coupler includes a body coupled to one end of the first shaft and a first protrusion protruding from the body in an axial direction of the first shaft, the first protrusion having a first surface and a second protrusion protruding from the first surface. The second protrusion is to lock with a groove to mount a cartridge on the frame, the first shaft is to provide a rotational force in a first rotational direction to rotate the second protrusion of the first coupler and to insert the second protrusion into the groove to lock with the cartridge, and the first surface of the first protrusion of the first coupler is to contact a second surface to transmit the rotational force to the second coupler in the first rotational direction.

Abstract: A developing cartridge attachable to a drum cartridge includes: a casing configured to accommodate developing agent therein; a developing roller rotatable about a developing roller axis extending in the first direction; a developing memory; and an electrical contact surface. The developing roller is positioned at one end of the casing in a second direction crossing the first direction. The electrical contact surface positioned at one end in the first direction of the casing and electrically connected to the developing memory. In a state where the developing cartridge is attached to the drum cartridge, the electrical contact surface of the developing cartridge is positioned between the developing roller and an electrical contact surface of the drum cartridge in the second direction.