A circular surgical stapling apparatus comprising: a body portion; a head portion disposed on a distal end of the body portion supporting a plurality of staples; an anvil assembly including an anvil, the anvil being movably supported in relation to the head portion between retracted and advanced positions, the anvil and the head portion defining a minimum tissue gap ("G") in the retracted position; an approximation assembly extending through the body portion and the head portion, the approximation assembly having a distal end supporting the anvil assembly and being actuable to move the anvil assembly relative to the head portion, the approximation assembly including a screw extension secured to a drive screw, the screw extension and the drive screw being adapted to be secured together in at least first and second orientations, wherein in the first orientation, the approximation assembly has a fixed first effective length and in the second orientation, the approximation assembly has a fixed second effective length, wherein the fixed first effective length is greater than the fixed second effective length, wherein in the first orientation, the anvil and the head portion define a first minimum tissue gap therebetween and in the second orientation, the anvil and the head portion define a second minimum tissue gap therebetween, characterised in that at least one of a distal end of the drive screw and a proximal end of the screw extension defines a first pair of openings and a second pair of openings, a central axis of the first pair of openings ("x1") being longitudinally spaced from a central axis of the second pair of openings ("x2"). a body portion; a head portion disposed on a distal end of the body portion supporting a plurality of staples; an anvil assembly including an anvil, the anvil being movably supported in relation to the head portion between retracted and advanced positions, the anvil and the head portion defining a minimum tissue gap ("G") in the retracted position; an approximation assembly extending through the body portion and the head portion, the approximation assembly having a distal end supporting the anvil assembly and being actuable to move the anvil assembly relative to the head portion, the approximation assembly including a screw extension secured to a drive screw, the screw extension and the drive screw being adapted to be secured together in at least first and second orientations, wherein in the first orientation, the approximation assembly has a fixed first effective length and in the second orientation, the approximation assembly has a fixed second effective length, wherein the fixed first effective length is greater than the fixed second effective length, wherein in the first orientation, the anvil and the head portion define a first minimum tissue gap therebetween and in the second orientation, the anvil and the head portion define a second minimum tissue gap therebetween, characterised in that at least one of a distal end of the drive screw and a proximal end of the screw extension defines a first pair of openings and a second pair of openings, a central axis of the first pair of openings ("x1") being longitudinally spaced from a central axis of the second pair of openings ("x2").