A cartridge assembly comprising: a cartridge channel including a bottom wall and side walls defining a recess , each of the side walls having a first end secured to the bottom wall and a second end spaced from the bottom wall , the second end of each of the side walls defining a support surface ; a staple cartridge defining a longitudinal axis and including an upper wall defining a tissue contact surface and side walls , the upper wall extending radially outward of the side walls of the staple cartridge to define a longitudinally extending shoulder , the staple cartridge being dimensioned to be received within the recess of the cartridge channel , the staple cartridge including staples and pushers and defining an open end opposite the upper wall ; a support plate supported on the open end of the staple cartridge , the support plate having a bottom wall and first and second side walls that define a U-shaped channel that is dimensioned to receive the staple cartridge and be received within the recess of the cartridge channel , each of the first and second side walls of the support plate having a first end connected to the bottom wall of the support plate and a second end having a support flange , characterized in that the support flanges are supported on the support surfaces of the cartridge channel ; and in that the cartridge assembly further comprises compression members positioned so that when the staple cartridge is received within the recess of the cartridge channel , a compression member lies between each of the shoulders of the staple cartridge and the support flanges of the support plate , each of the compression members being formed from an elastic material. a cartridge channel including a bottom wall and side walls defining a recess , each of the side walls having a first end secured to the bottom wall and a second end spaced from the bottom wall , the second end of each of the side walls defining a support surface ; a staple cartridge defining a longitudinal axis and including an upper wall defining a tissue contact surface and side walls , the upper wall extending radially outward of the side walls of the staple cartridge to define a longitudinally extending shoulder , the staple cartridge being dimensioned to be received within the recess of the cartridge channel , the staple cartridge including staples and pushers and defining an open end opposite the upper wall ; a support plate supported on the open end of the staple cartridge , the support plate having a bottom wall and first and second side walls that define a U-shaped channel that is dimensioned to receive the staple cartridge and be received within the recess of the cartridge channel , each of the first and second side walls of the support plate having a first end connected to the bottom wall of the support plate and a second end having a support flange , characterized in that the support flanges are supported on the support surfaces of the cartridge channel ; and in that the cartridge assembly further comprises compression members positioned so that when the staple cartridge is received within the recess of the cartridge channel , a compression member lies between each of the shoulders of the staple cartridge and the support flanges of the support plate , each of the compression members being formed from an elastic material. <EOS>