If you compare the STC1816 to an original Supervac fitted to the Esprit Turbo, the mounting pattern looks the same, but the overall diameter is bigger on the Esprit (compare the 2 servos side by side looking at the square pressing with the 4 mounting studs) The STC1816 is flush with the outer diameter of the servo, the original has around 1/2" additional material beyond the pressing (1" approx overall larger diameter). Hope that makes sense... (maybe its different on the NA Esprit?)