Replace that original stripped or leaking burp plug on the coolant crossover tube. Includes new double o ring and is Black Anodized for corrosion resistance so it wont rust and seize like the original! Hex style cap to reduce stripping like the allen head factory cap makes the part easier to use. DOES NOT FIT AFTERMARKET CROSSOVER TUBES SUCH AS THOSE WITH PROCHARGER SUPERCHARGERS. DESIGNED ONLY FOR FACTORY CROSSOVER TUBES! THESE FIT DOHC : 96-04 Cobras, 03-04 Mach1, 93-98 Lincoln Mark VIII, 95-02 Lincoln Continental, 03-04 Mercury Marauder, 03-05 Lincoln Aviator