A cartridge for being detachable from and attachable to a main casing of an image forming apparatus, the cartridge comprising: a frame configured to accommodate therein developing agent; a rotation body having a rotation axis extending in a predetermined direction, the rotation body being provided at the frame and rotatable about the rotation axis relative to the frame; a driving force transmission unit provided at the frame and being suitable for transmitting an external driving force from the image forming apparatus to the rotation body; a gear cover main portion and a moving member suitable for being irreversibly moved to one of a covered position and an exposed position by the external driving force transmitted through the driving force transmission unit, the moving member comprising a cover portion which is configured to cover at least a portion of the driving force transmission unit when the moving member is at the covered position, and which is configured to expose the driving force transmission unit to the outside of the cartridge when the moving member is at the exposed position, characterized in that the gear cover main portion includes a detection opening and an exposure opening, the cover portion is interposed between the detection opening and the driving force transmission unit to cover the portion of the driving force transmission unit in the covered position of the moving member, and is not interposed between the detection opening and the driving force transmission unit to expose the driving force transmission unit through the detection opening in the exposed position of the moving member, the moving member further comprises a display portion which is exposed to the outside of the cartridge through the exposure opening in the exposed position and which is retracted from the exposure opening in the covered position. a frame configured to accommodate therein developing agent; a rotation body having a rotation axis extending in a predetermined direction, the rotation body being provided at the frame and rotatable about the rotation axis relative to the frame; a driving force transmission unit provided at the frame and being suitable for transmitting an external driving force from the image forming apparatus to the rotation body; a gear cover main portion and a moving member suitable for being irreversibly moved to one of a covered position and an exposed position by the external driving force transmitted through the driving force transmission unit, the moving member comprising a cover portion which is configured to cover at least a portion of the driving force transmission unit when the moving member is at the covered position, and which is configured to expose the driving force transmission unit to the outside of the cartridge when the moving member is at the exposed position, characterized in that the gear cover main portion includes a detection opening and an exposure opening, the cover portion is interposed between the detection opening and the driving force transmission unit to cover the portion of the driving force transmission unit in the covered position of the moving member, and is not interposed between the detection opening and the driving force transmission unit to expose the driving force transmission unit through the detection opening in the exposed position of the moving member, the moving member further comprises a display portion which is exposed to the outside of the cartridge through the exposure opening in the exposed position and which is retracted from the exposure opening in the covered position.