Dulux Once Eggshell has been specially formulated to give a perfect low sheen finish on interior and exterior primed or painted wood or metal surfaces in just one coat. It does not require an undercoat. For long term exterior protection, we recommend using a suitable primer such as the Dulux Multi-surface Primer & Undercoat or one of the Dulux Weathershield equivalents, such as the Dulux Weathershield Quick Dry Exterior range.