A fastener cartridge (2000, 3200, 3600, 3800, 4500) for use with a surgical instrument, wherein said fastener cartridge (2000, 3200, 3600, 3800, 4500) comprises: a cartridge body (2010, 3210, 3610, 3810, 4510), wherein a plurality of longitudinal rows of fastener cavities (2050, 3250, 3650, 3850) are defined into said cartridge body (2010, 3210, 3610, 3810, 4510), and wherein said cartridge body (2010, 3210, 3610, 3810, 4510) comprises: a deck (2011, 3213, 3613, 4511), wherein each of said fastener cavities (2050, 3250, 3650, 3850) comprises an opening in said deck (2011, 3213, 3613, 4511); a plurality of first extensions (2053, 3253) extending from said deck (2011, 3213, 3613, 4511), wherein each of said first extensions (2053, 3253) is positioned at least partially around a respective one of said openings in said deck (2011, 3213, 3613, 4511), and wherein each of said first extensions (2053, 3253) comprises a first shape; and a plurality of second extensions (2051, 3251, 3851) extending from said deck (2011, 3213, 3613, 4511), wherein each of said second extensions (2051, 3251, 3851) is positioned at least partially around a respective one of said openings in said deck (2011, 3213, 3613, 4511), and wherein each of said second extensions (2051, 3251, 3851) comprises a second shape that is different from said first shape; wherein each of said first extensions (2053, 3253) is positioned at least partially around the distal end of a respective opening in said deck (2011, 3213, 3613, 4511) corresponding to a distal-most fastener cavity of the plurality of said rows; and a plurality of fasteners removably positioned in said fastener cavities (2050, 3250, 3650, 3850); characterized in that said first shape of each of said first extensions (2053, 3253) differs from said second shape of each of said second extensions (2051, 3251, 3851) in that it comprises a distal sloped surface, extending from said deck to the top of said first extension (2053, 3253) and across the width of said first extension (2053, 3253), and configured to facilitate the insertion of tissue between the fastener cartridge (2000, 3200, 3600, 3800, 4500) and an anvil. a deck (2011, 3213, 3613, 4511), wherein each of said fastener cavities (2050, 3250, 3650, 3850) comprises an opening in said deck (2011, 3213, 3613, 4511); a plurality of first extensions (2053, 3253) extending from said deck (2011, 3213, 3613, 4511), wherein each of said first extensions (2053, 3253) is positioned at least partially around a respective one of said openings in said deck (2011, 3213, 3613, 4511), and wherein each of said first extensions (2053, 3253) comprises a first shape; and a plurality of second extensions (2051, 3251, 3851) extending from said deck (2011, 3213, 3613, 4511), wherein each of said second extensions (2051, 3251, 3851) is positioned at least partially around a respective one of said openings in said deck (2011, 3213, 3613, 4511), and wherein each of said second extensions (2051, 3251, 3851) comprises a second shape that is different from said first shape; wherein each of said first extensions (2053, 3253) is positioned at least partially around the distal end of a respective opening in said deck (2011, 3213, 3613, 4511) corresponding to a distal-most fastener cavity of the plurality of said rows; and a plurality of fasteners removably positioned in said fastener cavities (2050, 3250, 3650, 3850); characterized in that said first shape of each of said first extensions (2053, 3253) differs from said second shape of each of said second extensions (2051, 3251, 3851) in that it comprises a distal sloped surface, extending from said deck to the top of said first extension (2053, 3253) and across the width of said first extension (2053, 3253), and configured to facilitate the insertion of tissue between the fastener cartridge (2000, 3200, 3600, 3800, 4500) and an anvil.