A staple can include a bridge and two pairs of opposed legs that connect to the bridge. A first pair of legs can connect to the bridge toward a first end at a first shoulder and a second shoulder. A second pair of legs, opposed to the first pair legs, can connect to the bridge toward a second end at a third shoulder. The bridge can include a substantially smooth and non-breaking top surface that transitions downwardly at the first end and the second end to outer surfaces of the first pair of legs and the second pair of legs. The bridge can include a substantially constant moment of inertia, which may help improve performance and reduce risk of staple breakage.