An image forming apparatus cartridge includes a casing and a developer roller having an axis L1, with the developer roller being rotatably supported in the casing to permit rotation about the axis L1. The cartridge also includes a first gear connected to the developer roller and a second gear in meshing engagement with the first gear. The cartridge further includes a coupling member having an axis L2, with the coupling member having (i) a first end portion connected to the second gear and operatively connected with the developer roller so as to be capable of transmitting a rotational force to the developer roller via the first and second gears, (ii) a second end portion having a recess formed therein and including at least two projections provided at diametrically opposed positions, and (iii) a connecting portion connecting the first end portion and the second end portion.