A toner cartridge according to one example embodiment includes a housing having a reservoir for holding toner. An outlet port is positioned on the front of the housing for transferring toner from the reservoir to the developer unit through an inlet port on the developer unit. A first engagement member projecting from the front of the housing is positioned to provide an initial force to begin to open a shutter on the inlet port of the developer unit as the toner cartridge is inserted in the image forming device. A second engagement member projecting from the front of the housing is spaced toward one of the sides of the housing from the first engagement member and positioned to provide a force to continue to open the shutter on the inlet port of the developer unit as the toner cartridge is inserted further in the image forming device.