A toner cartridge according to one example embodiment includes a housing having a reservoir for containing toner therein. An exit port in fluid communication with the reservoir faces downward on a front of the housing near a first side of the housing. A portion of a main interface gear for providing rotational power to a toner delivery system is exposed on the front of the housing near a top of a second side of the housing and engagable with a corresponding drive gear in the image forming device. A projection extends forward from the housing further forward than a frontmost portion of the exit port and is spaced from the exit port toward the first side of the housing. A front of the projection is unobstructed for engaging a developer unit when the toner cartridge is inserted into the image forming device.