Dicor Ultra Sealant Primer is a solvent-based primer to be used in preparation of sealing TPO and EPDM membranes and polypropylene plastic rooftop accessories with Dicor Ultra Sealant. Read all instructions carefully before priming your RV roof. NOTE: Dicor Ultra Sealant Primer is not to be used on plastics under stress, such as polycarbonate skylights. Not to be used on plastics under stress, such as polycarbonate skylights | Dicor Ultra Sealant Primer, Pint