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"). <EOS>