OPI Natural Nail Base Coat. Size 15ml/0.5 oz. Proper application is key to making nail polish last, be sure to start with properly prepped nails and apply 1 coat of base coat nail polish before color application to help extend wear. OPI Natural Nail Base Coat nail polish can be used under OPI Nail Lacquer shades. Promotes a longer-lasting manicure for optimal results and up to 7 days of wear and shine.