An ink cartridge includes a particular wall, a protruding member extending from the particular wall in a particular direction, a protrusion extending from the particular wall in the particular direction, and an ink chamber configured to store ink therein. The ink cartridge also includes a translucent portion defining an enclosure, an ink supply portion configured to supply ink from an interior of the ink chamber to an exterior of the ink chamber, in which the ink supply portion and the translucent portion are each positioned between the protrusion and the protruding member. The ink cartridge further includes a signal blocking member positioned within the enclosure. Moreover, the signal blocking member is configured to move within the enclosure based at least on an amount of ink disposed within the ink chamber, and the signal blocking member is sandwiched between the at least one pair of wall surfaces.