a developing roller rotatable about a first axis extending in a first direction, the developing roller including a developing roller shaft;
a housing configured to accommodate developer therein, the housing having one end portion and another end portion separated from the one end portion in the first direction;
a coupling rotatable about a second axis extending in the first direction, the coupling being positioned at the one end portion of the housing;
a shaft movable according to rotation of the coupling; and
a detection protrusion positioned at the another end portion of the housing, the detection protrusion being movable according to the movement of the shaft, the detection protrusion being made of a conductive material.