A cartridge mountable in an image forming apparatus includes a rotatable member, a hollow cylindrical portion, having first and second inner grooves, that transmits a rotational force to the rotatable member, a coupling member having a spherical base portion and an axially movable pin penetrating the spherical base portion and having first and second end portions projected outside the base portion, and a limiting portion, provided in the first inner groove, for limiting axial movement of the pin. When the coupling member is inclined to a maximum extent within a predetermined inclination range, after movement of the pin is limited, so that the first end portion moves away, and the second end portion moves toward, the rotatable member, the first end portion is disengaged from the first inner groove, whereas the second end portion is engaged with the second inner groove.