A staple cartridge assembly, comprising: a cartridge body, comprising: a deck comprising a proximal end and a distal end; a longitudinal slot defined in said deck, wherein said longitudinal slot is configured to receive a firing member; a first longitudinal row of staple cavities; and a second longitudinal row of staple cavities (434a; 434b), wherein said first and second longitudinal rows of staples cavities are laterally offset; a sled movable toward said distal end by the firing member during a firing stroke; a plurality of first staples, wherein one of said first staples is removably stored in each staple cavity of said first longitudinal row, wherein each said first staple is comprised of a bent wire; a plurality of staple drivers configured to support said first staples, wherein said sled is configured to engage said staple drivers to eject said first staples from said first longitudinal row of staple cavities during the firing stroke; and a plurality of second staples formed from flat stock; characterized in that one of said second staples is removably stored in each staple cavity (434a; 434b) of said second longitudinal row, wherein each said second staple comprises an integrally-formed driver, and wherein said sled is configured to directly engage said integrally-formed drivers of said second staples and eject said second staples from said second longitudinal row of staple cavities (434a; 434b) during the firing stroke. a cartridge body, comprising: a deck comprising a proximal end and a distal end; a longitudinal slot defined in said deck, wherein said longitudinal slot is configured to receive a firing member; a first longitudinal row of staple cavities; and a second longitudinal row of staple cavities (434a; 434b), wherein said first and second longitudinal rows of staples cavities are laterally offset; a deck comprising a proximal end and a distal end; a longitudinal slot defined in said deck, wherein said longitudinal slot is configured to receive a firing member; a first longitudinal row of staple cavities; and a second longitudinal row of staple cavities (434a; 434b), wherein said first and second longitudinal rows of staples cavities are laterally offset; a sled movable toward said distal end by the firing member during a firing stroke; a plurality of first staples, wherein one of said first staples is removably stored in each staple cavity of said first longitudinal row, wherein each said first staple is comprised of a bent wire; a plurality of staple drivers configured to support said first staples, wherein said sled is configured to engage said staple drivers to eject said first staples from said first longitudinal row of staple cavities during the firing stroke; and a plurality of second staples formed from flat stock; characterized in that one of said second staples is removably stored in each staple cavity (434a; 434b) of said second longitudinal row, wherein each said second staple comprises an integrally-formed driver, and wherein said sled is configured to directly engage said integrally-formed drivers of said second staples and eject said second staples from said second longitudinal row of staple cavities (434a; 434b) during the firing stroke.