This is the third generation contoured dog used on extruded aluminum framed Bomar hatches built after November 2007. They are found on many later Catalinas. Check the photo carefully. If yours has the gray flip lock which prevents the hatch from being opened from the exterior of the boat, this is the correct part.
Some larger Catalinas used a similar hatch built by Lewmar but the dogs are different than those pictured. Caution: The designation "Left" is molded into the top side of the handle where it can only be seen through the lens. "Left" is relative to the hatch (not the boat) when viewed looking into an open hatch. In the case of a trapezoidal forward hatch, while facing aft, on the outside of the boat, the "Left" handle is on the starboard side of the boat!