cutting member 120 similar to the above endocutter 800 can further include a drive bar for advancing cutting member 120 within slot 864 of staple cartridge 812 however owing to the direction and degree of the curvature of staple cartridge 812 some drive bars may be largely unsuitable for use with endocutter 700 or 800 for example more particularly the illustrated drive bars 126 and 226 in fig4 and 24 respectively owing to their cross sectional geometries may not be particularly well suited to flex in a substantially downward or substantially upward direction as required by endocutters 700 and 800 respectively referring to fig2 for example the illustrated cross section of drive bar 226 is substantially rectangular and is defined by height 257 and width 259 as illustrated in fig2 height 257 is substantially greater than width 259 and as a result the cross section of the illustrated drive bar 226 has a moment of inertia with respect to height 257 that is substantially greater than the moment of inertia with respect to width 259 accordingly the illustrated drive bar 226 is substantially less flexible with respect to height 257 than width 259 and may not be able to sufficiently bend in the substantially downward.