A printing fluid cartridge configured to be inserted into a cartridge mounting portion in an upright position in an insertion direction against a biasing force exerted in a removal direction opposite the insertion direction, wherein the printing fluid cartridge in the upright position has a width in a width direction, a height in a height direction, and a depth in a depth direction, wherein the width direction, the height direction, and the depth direction are perpendicular to each other and the depth direction is parallel with the insertion direction, and when the printing fluid cartridge is in the upright position, the height direction corresponds to the gravitational direction; wherein the printing fluid cartridge comprises: a front face oriented toward the insertion direction when the printing fluid cartridge is inserted into the cartridge mounting portion; a rear face positioned opposite the front face with respect to the insertion direction and oriented toward the removal direction when the printing fluid cartridge is inserted into the cartridge mounting portion; a chamber positioned between the front face and the rear face and configured to store printing fluid therein; a printing fluid supply portion positioned at the front face and comprising a printing fluid supply opening, wherein the printing fluid supply portion is configured to supply the printing fluid from an interior of the chamber to an exterior of the chamber via the printing fluid supply opening; at least one electrical interface (75, 76, 77) positioned between the front face and the rear face and configured to be electrically connected to at least one contact of the cartridge mounting portion; and an engagement surface configured to contact an engagement member of the cartridge mounting portion, such that the printing fluid cartridge is retained in the cartridge mounting portion against the biasing force, wherein when the printing fluid cartridge is in the upright position, the at least one electrical interface (75, 76, 77) and the engagement surface are both are configured to be accessed from an exterior of the printing fluid cartridge in the height direction and are positioned at or adjacent to a top face of the printing fluid cartridge which extends between the front face and the rear face and faces upward in the height direction, the at least one electrical interface (75, 76, 77) is positioned more forward than the engagement surface with respect to the insertion direction, and the at least one electrical interface (75, 76, 77) and the engagement surface intersect a plane which is parallel with the insertion direction and the height direction; and wherein the at least one electrical interface (75, 76, 77) is positioned above at least a portion of the engagement surface when the printing fluid cartridge is in the upright position. a front face oriented toward the insertion direction when the printing fluid cartridge is inserted into the cartridge mounting portion; a rear face positioned opposite the front face with respect to the insertion direction and oriented toward the removal direction when the printing fluid cartridge is inserted into the cartridge mounting portion; a chamber positioned between the front face and the rear face and configured to store printing fluid therein; a chamber positioned between the front face and the rear face and configured to store printing fluid therein; a printing fluid supply portion positioned at the front face and comprising a printing fluid supply opening, wherein the printing fluid supply portion is configured to supply the printing fluid from an interior of the chamber to an exterior of the chamber via the printing fluid supply opening; at least one electrical interface (75, 76, 77) positioned between the front face and the rear face and configured to be electrically connected to at least one contact of the cartridge mounting portion; and an engagement surface configured to contact an engagement member of the cartridge mounting portion, such that the printing fluid cartridge is retained in the cartridge mounting portion against the biasing force, wherein when the printing fluid cartridge is in the upright position, the at least one electrical interface (75, 76, 77) and the engagement surface are both are configured to be accessed from an exterior of the printing fluid cartridge in the height direction and are positioned at or adjacent to a top face of the printing fluid cartridge which extends between the front face and the rear face and faces upward in the height direction, the at least one electrical interface (75, 76, 77) is positioned more forward than the engagement surface with respect to the insertion direction, and the at least one electrical interface (75, 76, 77) and the engagement surface intersect a plane which is parallel with the insertion direction and the height direction; and wherein the at least one electrical interface (75, 76, 77) is positioned above at least a portion of the engagement surface when the printing fluid cartridge is in the upright position.