A cartridge (B) dismountable from a main assembly (A) of an electrophotographic image forming apparatus including a rotatable main assembly side engaging portion , said cartridge (B) comprising: i) a rotatable member capable of carrying a developer (t) and having a rotational axis (L1) extending in a direction substantially perpendicular to a dismounting direction of said cartridge (B); ii) a coupling member provided at one end portion of said cartridge (B) with respect to the rotational axis (L1) to transmit a rotational force from the main assembly side engaging portion to said rotatable member ; and iii) a rotational force transmission member for transmitting the rotational force from said coupling member toward said rotatable member , wherein the rotational force transmission member includes a hollow portion , wherein said coupling member is movable between a first position in which the rotational axis (L181) of said coupling member is substantially parallel with the rotational axis (L1) of said rotatable member , and a second position, in which said coupling member is displaced from the first position in a direction of the rotational axis (L1) of said rotatable member toward the other end portion of said cartridge (B), characterized in that in said second position, the rotational axis (L181) of said coupling member is substantially parallel with the rotational axis (L1) of said rotatable member and in said second position, said coupling member is displaced, inside of said hollow portion as seen along the axis (L181) of said coupling member , from the first position in a direction perpendicular to the rotational axis (L1) of said rotatable member , and one of said coupling member and said rotational force transmission member is provided with an inclined portion, and the other of said coupling member and said rotational force transmission member is provided with a contact portion contactable to the inclined portion. i) a rotatable member capable of carrying a developer (t) and having a rotational axis (L1) extending in a direction substantially perpendicular to a dismounting direction of said cartridge (B); ii) a coupling member provided at one end portion of said cartridge (B) with respect to the rotational axis (L1) to transmit a rotational force from the main assembly side engaging portion to said rotatable member ; and iii) a rotational force transmission member for transmitting the rotational force from said coupling member toward said rotatable member , wherein the rotational force transmission member includes a hollow portion , wherein said coupling member is movable between a first position in which the rotational axis (L181) of said coupling member is substantially parallel with the rotational axis (L1) of said rotatable member , and a second position, in which said coupling member is displaced from the first position in a direction of the rotational axis (L1) of said rotatable member toward the other end portion of said cartridge (B), characterized in that in said second position, the rotational axis (L181) of said coupling member is substantially parallel with the rotational axis (L1) of said rotatable member and in said second position, said coupling member is displaced, inside of said hollow portion as seen along the axis (L181) of said coupling member , from the first position in a direction perpendicular to the rotational axis (L1) of said rotatable member , and one of said coupling member and said rotational force transmission member is provided with an inclined portion, and the other of said coupling member and said rotational force transmission member is provided with a contact portion contactable to the inclined portion. <EOS>