This is a fuel filler neck grommet for your 1999-04 Mustang. This part seal the filler neck into the fuel tank. Over time these can become brittle and begin to leak fuel. Get yours replaced and get your Mustang back on the road!
I would like to give a big thank you to Latemodel Resto Employee Tyler Rodriguez, he went above and beyond to provide outstanding Customer service, really made me a customer for life, i plan to make all my future purchases from latemodelresto when i get my hands on a 2015 Mustang. thanks again Tyler for the outstanding customer service you and latemodelresto provide.