Dress up the engine compartment of your Mustang with a ROUSH Billet Radiator Cap. The billet radiator cap is made from high-quality billet aluminum for its appearance, corrosion resistance, and strength to weight ratio. The radiator cap is manufactured in the USA using high precision CNC machining for precise fitment. Once machined, the radiator cap is polished for a sleek appearance. The ROUSH billet radiator cap slides over the existing cap and is held in place with automotive-grade double-sided tape.