COMPATIBILITY: Fit for 1998-2004 Ford F-250 F-350 F-450 and F-550 4X4s having the vacuum-operated front axle. SUPERIOR QUALITY: Constructed from Heavy Duty Steel, our product has high toughness and shows its advantage in rust-resistance and durability. A MUST-HAVE TOOL: This tool helps vacuum locking hubs work after replacing the axle seals since it prevents front hub vacuum leaks that would cause the 4WD not engage. EASY INSTALLATION: Installing the seal onto the axle shaft and into the wheel knuckle, you just need to evenly apply pressure to the whole units while you push it on. .