Drum Unit

A drum unit, comprising:

• a casing, to which a developer cartridge comprising a developer roller and a protrusion that protrudes in an axial direction of the developer roller is attachable;
• a photosensitive drum;
• a first guide arranged to confront the protrusion of the developer cartridge along an orthogonal direction orthogonal to the axial direction in a state where the developer cartridge is attached to the casing;
• a second guide movable between a first position and a second position being closer to the first guide than the first position, the second guide being arranged to confront the protrusion of the developer cartridge along the orthogonal direction in the state where the developer cartridge is attached to the casing;
• and
• an urging member configured to urge the second guide to allow the second guide to move from the first position toward the second position,
• wherein the second guide comprises a contact part configured to contact the first guide in a state where the second guide is located in the second position.