Abstract: A replaceable staple cartridge comprising a cartridge body, staples, and a staple cartridge tray secured to the staple cartridge body is disclosed. The cartridge body comprises a first longitudinal slot, a deck, and first sides extending downwardly from the deck, wherein an edge is defined between each first side and the deck. The cartridge body further comprises staple cavities defined in said deck and recesses defined in the deck proximal to the staple cavities. The staple cartridge tray comprises a bottom comprising a second longitudinal slot defined therein and second sides extending upwardly from the bottom, wherein each second side comprises a proximal end including a projection, wherein each second side is adjacent to a first side, and wherein each projection wraps around an edge and extends downwardly into a recess defined in the deck.