OPI Powder Perfection Base Coat: The resin base coat is the essential first step to all OPI Powder Perfection applications, it provides optimal adhesion of powders to nails, and helps ensure long-lasting results. The fan-favorite OPI pro-wide brush is now in the base coat and the flat bristles allow for perfect product pick up and precise application around the cuticle, and as always -- is odor-free. Making it ideal for clean air salon environments.