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.