A printing material supply system includes a printing device and a cartridge. The printing device has a cartridge mounting structure. The cartridge is removably attached to the cartridge mounting structure. The cartridge mounting structure has a device-side terminal, a lever, a first device-side locking element and a second device-side locking element. The device-side terminal is configured to contact with a cartridge-side terminal. The first device-side locking element is configured as part of the lever. The second device-side locking element is configured to engage with a second locking surface of a second cartridge-side locking element. The cartridge-side terminal has a cartridge-side contact portion configured to be in contact with the device-side terminal. The cartridge-side contact portion is provided on the negative Z-axis side of the second locking surface.