Product Feature: * Application: Works on 1998-2004 FOMOCO F-250 F-350 F-450 and F-550 4X4s having the vacuum-operated front axle. * Undamaged And Prevent From Leaking: Ensure the seal is installed properly and undamaged, both onto the axle shaft and into the wheel knuckle, Prevents front hub vacuum leaks that would cause the 4WD to not engage. * Superior Quality: Solid one piece steel construction with black oxide finish resisting rust and impact, ensures reliable long-term service. * A Must Have Tool: Must have for seal replacement on your FOMOCO Super-duty, makes final assembly simple and quick and accurate. .