A drum unit usable in the process cartridge includes a photosensitive drum having an axis L1, a drum flange provided at an end of the photosensitive drum, with a part of the drum flange being positioned within the photosensitive drum, and a coupling member having an axis L2. The coupling member includes (i) a first end portion at least a part of which is positioned within the drum flange, and (ii) a second end portion including (ii-i) a surface recessed in the second end portion and facing away from the first end portion and (ii-ii) at least one projection projecting from a surface adjacent to the recessed surface, and (iii) a connecting portion connecting the first end portion and the second end portion.