A staple cartridge for use with a surgical instrument, wherein said staple cartridge comprises: a proximal end; a distal end; a cartridge body comprising a tissue-supporting surface; an elongate slot extending from said proximal end toward said distal end, wherein said elongate slot defines a longitudinal axis; a first longitudinal row of staple cavities extending alongside said elongate slot; a second longitudinal row of staple cavities extending alongside said first longitudinal row of staple cavities; a third longitudinal row of staple cavities extending alongside said second longitudinal row of staple cavities; staples removably stored in said staple cavities (13100, 13200, 13300); staple drivers removably positioned within said staple cavities, wherein each said staple driver comprises: a first staple-supporting member positioned within a said staple cavity from said first longitudinal row; a second staple-supporting member positioned within a said staple cavity from said second longitudinal row; and a third staple-supporting member positioned within a said staple cavity from said third longitudinal row; a firing member movable along said elongate slot between said proximal end and said distal end, wherein said firing member is configured to motivate said staple drivers from an unfired position to a fired position during a staple firing stroke; and driver retention members configured to engage said staple drivers when said staple drivers are in said fired position characterised in that: each driver retention member comprises a flexible tab and a first projection extending from the tab wherein each driver retention member is resiliently biased such that each first projection is biased into engagement with a respective aperture defined in each of said staple drivers when said staple drivers are in said fired position to retain said staple drivers in said fired position. a proximal end; a distal end; a cartridge body comprising a tissue-supporting surface; an elongate slot extending from said proximal end toward said distal end, wherein said elongate slot defines a longitudinal axis; a first longitudinal row of staple cavities extending alongside said elongate slot; a second longitudinal row of staple cavities extending alongside said first longitudinal row of staple cavities; a third longitudinal row of staple cavities extending alongside said second longitudinal row of staple cavities; staples removably stored in said staple cavities (13100, 13200, 13300); staple drivers removably positioned within said staple cavities, wherein each said staple driver comprises: a first staple-supporting member positioned within a said staple cavity from said first longitudinal row; a second staple-supporting member positioned within a said staple cavity from said second longitudinal row; and a third staple-supporting member positioned within a said staple cavity from said third longitudinal row; a first staple-supporting member positioned within a said staple cavity from said first longitudinal row; a second staple-supporting member positioned within a said staple cavity from said second longitudinal row; and a third staple-supporting member positioned within a said staple cavity from said third longitudinal row; a firing member movable along said elongate slot between said proximal end and said distal end, wherein said firing member is configured to motivate said staple drivers from an unfired position to a fired position during a staple firing stroke; and driver retention members configured to engage said staple drivers when said staple drivers are in said fired position characterised in that: each driver retention member comprises a flexible tab and a first projection extending from the tab wherein each driver retention member is resiliently biased such that each first projection is biased into engagement with a respective aperture defined in each of said staple drivers when said staple drivers are in said fired position to retain said staple drivers in said fired position.