A surgical stapler, comprising: a handle (102', 104'); a staple cartridge channel configured to receive a staple cartridge; a distally moveable pusher bar assembly configured to advance a staple sled assembly within the staple cartridge and along a longitudinal axis of the surgical stapler to deploy staples from the staple cartridge; and an anvil assembly, said anvil assembly comprising: an anvil channel; an anvil comprising a positioning surface and a staple forming surface, wherein the anvil is movable relative to said anvil channel to vary the distance between said positioning surface of said anvil and said anvil channel; and an adjustment member movably positioned intermediate said anvil channel and said anvil, wherein said adjustment member has a first diameter and a second diameter, wherein said second diameter is different than said first diameter, and wherein said adjustment member is rotatable about an axis between a first position and a second position to selectively position one of said first diameter and said second diameter intermediate said anvil channel and said positioning surface of said anvil; characterized in that the axis about which the adjustment member is configured to be rotated an axis parallel to said longitudinal axis the surgical stapler; and said adjustment member limits the movement of said anvil toward said anvil channel such that the minimum distance between said positioning surface of said anvil and said anvil channel is defined by said first diameter in said first position of said adjustment member and by said second diameter in said second position of said adjustment member. a handle (102', 104'); a staple cartridge channel configured to receive a staple cartridge; a distally moveable pusher bar assembly configured to advance a staple sled assembly within the staple cartridge and along a longitudinal axis of the surgical stapler to deploy staples from the staple cartridge; and an anvil assembly, said anvil assembly comprising: an anvil channel; an anvil comprising a positioning surface and a staple forming surface, wherein the anvil is movable relative to said anvil channel to vary the distance between said positioning surface of said anvil and said anvil channel; and an adjustment member movably positioned intermediate said anvil channel and said anvil, wherein said adjustment member has a first diameter and a second diameter, wherein said second diameter is different than said first diameter, and wherein said adjustment member is rotatable about an axis between a first position and a second position to selectively position one of said first diameter and said second diameter intermediate said anvil channel and said positioning surface of said anvil; an anvil channel; an anvil comprising a positioning surface and a staple forming surface, wherein the anvil is movable relative to said anvil channel to vary the distance between said positioning surface of said anvil and said anvil channel; and an adjustment member movably positioned intermediate said anvil channel and said anvil, wherein said adjustment member has a first diameter and a second diameter, wherein said second diameter is different than said first diameter, and wherein said adjustment member is rotatable about an axis between a first position and a second position to selectively position one of said first diameter and said second diameter intermediate said anvil channel and said positioning surface of said anvil; characterized in that the axis about which the adjustment member is configured to be rotated an axis parallel to said longitudinal axis the surgical stapler; and said adjustment member limits the movement of said anvil toward said anvil channel such that the minimum distance between said positioning surface of said anvil and said anvil channel is defined by said first diameter in said first position of said adjustment member and by said second diameter in said second position of said adjustment member.