A monochrome cartridge without an electrophotographic photosensitive drum (107; 9107) for use with a main assembly of an electrophotographic image forming apparatus, said main assembly including a driving shaft (180; 1180; 1280) having a rotational force applying portion, wherein said cartridge is dismountable from the main assembly in a direction substantially perpendicular to an axial direction of the driving shaft (180; 1180; 1280), said cartridge comprising: i) a developing roller (110; 6110; 9110) for developing an electrostatic latent image formed on the electrophotographic photosensitive drum (107; 9107), said developing roller (110; 6110; 9110) being rotatable about an axis thereof; and ii) a coupling member (150; 12150; 1150; 1350; 14150; 4150; 7150; 6150; 9150) adapted to be engageable with said rotational force applying portion to receive a rotational force for rotating said developing roller (110; 6110; 9110), said coupling member (150; 12150; 1150; 1350; 14150; 4150; 7150; 6150; 9150) adapted to be capable of taking a rotational force transmitting angular position for transmitting the rotational force for rotating said developing roller (110; 6110; 9110) to said developing roller (110; 6110; 9110) and a disengaging angular position in which said coupling member (150; 12150; 1150; 1350; 14150; 4150; 7150; 6150; 9150) is inclined away from said rotational force transmitting angular position, characterised in that said cartridge is configured such that when said cartridge is dismounted from the main assembly of the electrophotographic image forming apparatus in a direction substantially perpendicular to the axis of said developing roller (110; 6110; 9110), said coupling member (150; 12150; 1150; 1350; 14150; 4150; 7150; 6150; 9150) moves from said rotational force transmitting angular position to said disengaging angular position and wherein guides (140R1, 140R2, 140L1, 140L2) project from said cartridge at lengthwise side surfaces and are adapted to guide said cartridge during dismounting in such a manner that the coupling member (150; 12150; 1150; 1350; 14150; 4150; 7150; 6150; 9150) gradually inclines in a direction which is away from said rotational force transmitting angular position toward the disengaging position. i) a developing roller (110; 6110; 9110) for developing an electrostatic latent image formed on the electrophotographic photosensitive drum (107; 9107), said developing roller (110; 6110; 9110) being rotatable about an axis thereof; and ii) a coupling member (150; 12150; 1150; 1350; 14150; 4150; 7150; 6150; 9150) adapted to be engageable with said rotational force applying portion to receive a rotational force for rotating said developing roller (110; 6110; 9110), said coupling member (150; 12150; 1150; 1350; 14150; 4150; 7150; 6150; 9150) adapted to be capable of taking a rotational force transmitting angular position for transmitting the rotational force for rotating said developing roller (110; 6110; 9110) to said developing roller (110; 6110; 9110) and a disengaging angular position in which said coupling member (150; 12150; 1150; 1350; 14150; 4150; 7150; 6150; 9150) is inclined away from said rotational force transmitting angular position,