RP 413 Grey primer is a versatile and widely used undercoat that prepares surfaces for painting while improving the appearance, durability, and finish of the final coat. It is commonly used on metal, wood, plastic, walls, automobiles, machinery, and many other surfaces. Although primer is available in several colors, grey primer has become particularly popular because of its neutral tone and ability to work effectively under both light and dark topcoats. The main purpose of grey primer is to create a suitable surface for the final paint. Many surfaces are uneven, porous, rough, or difficult for paint to adhere to directly.