A process cartridge is detachably mountable to a main assembly of an electrophotographic image forming apparatus. The cartridge includes a frame; an electrophotographic photosensitive drum; a developing device for developing an electrostatic latent image formed on the drum; a developer accommodating portion for accommodating a developer for developing the latent image; a developer supply opening for supplying the developer from the accommodating portion to the developing device; a for unsealably sealing the opening; a grip member for being gripped when the sealing member is pulled to unseal the opening; and a grip member mounting portion separably mounted on the frame. The grip member has a stopper for preventing the cartridge from entering the main assembly by abutment to a part of the main assembly when the cartridge is being mounted to the main assembly with the sealing member mounted on the frame.