Printing-fluid cartridge having interfering surface, and set of the printing-fluid cartridges

A set of printing-fluid cartridges each defining a depthwise direction, a height direction perpendicular to the depthwise direction, and a widthwise direction perpendicular to the depthwise direction and the height direction, each of the printing-fluid cartridges comprising:

• a housing comprising:
• a lower case defining therein a storage chamber configured to store printing fluid;
• a supply portion provided at the lower case and having a liquid passage extending in the depthwise direction to be in communication with the storage chamber;
• an upper cover in engagement with the lower case, the upper cover being positioned upward relative to the storage chamber in the height direction and having an upper surface facing upward in the height direction, the upper surface defining a widthwise center in the widthwise direction;
• an electrical interface supported by the upper cover;
• and
• a protrusion provided at the upper cover, the protrusion extending in the depthwise direction, the protrusion being positioned opposite the supply portion with respect to the storage chamber in the height direction,
• the set of printing-fluid cartridges comprising:
• a first printing-fluid cartridge storing printing fluid of a first type;
• and
• a second printing-fluid cartridge storing printing fluid of a second type different from the first type,
• wherein the protrusion of the first printing-fluid cartridge and the protrusion of the second printing-fluid cartridge are at different positions from each other with respect to the widthwise center of the upper surface in the widthwise direction.