An ink cartridge may have an ink accommodating portion shaped to contain ink, an ink supply hole disposed at a bottom of the ink accommodating portion, and a valve unit including a movable valve portion and a fixed valve portion, the movable valve portion being oriented such that a flow of ink is regulated by a horizontal motion of the movable valve portion. The valve unit may further include a main portion and an auxiliary portion, the movable valve portion being disposed on the main portion and the fixed valve portion being disposed on the auxiliary portion, wherein the auxiliary portion is selectively detachable from the main portion. The ink cartridge may further comprise a supply hole attachment located at the bottom of the ink accommodating portion, the supply hole being defined in a selectively detachable supply hole attachment.