Abstract: A shuttle matrix printer cartridge has a housing for storing the ribbon, an exit arm, an entrance arm spaced from the exit arm and a drive mechanism for removing ribbon from the storage chamber through the exit arm into position for printing between a printhead and a substrate and reentry into the cartridge through the entrance arm. The entrance arm is flexible in the plane of the cartridge toward and away from the exit arm to facilitate changes in ribbon drag produced during high dot density printing. The cartridge has three spacer legs along its underside for supporting the cartridge on the printer platform in use. Additionally, a post engages a recess in the exit arm to maintain the latter arm rigid during use, while such post, in conjunction with a drive shaft carried by the printer and received in a cartridge drive wheel, positions the cartridge in the printer against lateral movement.