Unique design helps prevent breakage by locking the plug porcelain core to the plug hex allowing it to turn as one complete unit. Will also pull plug porcelain core if plug hex only is removed. Detailed Instructions to maximize success rate. Works on: Ford 4.6L 3V V8 engines used in 2005-2008 Mustang, 2006-2008 Explorer. Ford 5.4L 3V V8 engines used in 2004-2008 F-Series, 2005-2008 Expedition, 2005-2008 Lincoln Navigator. Ford 6.8L 3V V10 engines used in 2005-2008 F-Series 250-350-450.