This genuine 1999 Ford Mustang gas cap is an essential replacement part that ensures your classic pony car's fuel system operates at peak performance. Designed specifically for the '99 Mustang's air and fuel delivery system, this OEM-quality gas cap creates a proper seal to maintain correct fuel tank pressure, prevent fuel evaporation, and keep contaminants out of your tank. Whether you're restoring your Mustang to factory specifications or simply need to replace a worn or missing cap, this part maintains the integrity of your vehicle's emissions system while preserving that authentic Ford look. Don't let a faulty gas cap trigger your check engine light or compromise your fuel efficiency – invest in this reliable replacement that's built to Ford's original specifications and will keep your '99 Mustang running smoothly for years to come.