If you're replacing your 2000-04 Mustang vapor valve, then it's a must to replace the vapor valve seal. Over time this seal rots and deteriorates causing fumes and fuel to leak through. This original replacement will get you back in business to do the job right! The vapor valve seal goes into the tank and holds the vapor valve in place. Look no further than Latemodel Restoration for all of the Mustang parts you're looking for!