15 fl. oz. Gray 2-in-1 Aerosol Primer (4603) by Transtar®. 2 in 1 Primers are a specialty coating designed for easy and convenient priming of metal and plastic parts. These primers help prevent rust and seal out moisture, while providing a smooth base for topcoat application on metal substrates. 2 in 1 Primers also have excellent flexibility and adhesion properties that enable them to be applied to flexible and rigid parts. 2 in 1 Primers are fast drying, provide superior fill and build, and are easy to sand. They are compatible with virtually all automotive paints.