Image forming apparatus

A cartridge apparatus, comprising:

• a drum cartridge including a photosensitive drum rotatable about a first axis extending in an axial direction;
• the drum cartridge configured to be received in a slot of an image forming apparatus, the slot extending in the axial direction and located below an intermediate transfer belt of the image forming apparatus;
• the drum cartridge having a lower surface configured to interact with a first guide rail positioned in the slot to guide the drum cartridge when the drum cartridge is inserted into the slot or removed from the slot in the axial direction;
• a developing cartridge including a developing roller rotatable about a second axis extending in the axial direction and a developing casing configured to accommodate toner therein, the developing cartridge configured to be received in the slot alongside the drum cartridge in an arrangement direction perpendicular to the axial direction;
• the developing cartridge having a lower surface configured to interact with a second guide rail separated from the first guide rail in the arrangement direction by a first distance to guide the developing cartridge when the developing cartridge is inserted into the slot or removed from the slot in the axial direction;
• and
• the developing casing including a side wall extending in the axial direction, the side wall configured to interact with first and second inner surfaces of the slot that are spaced apart from one another in the axial direction and separated from the first guide rail in the arrangement direction by a distance greater than the first distance to press the developing roller toward the photosensitive drum in the arrangement direction in a state where the drum cartridge and the developing cartridge are received in the slot.