Roller covers are the fluffy tubes that you insert on the roller mechanism. Covers with a thicker nap hold more paint and are best for pitted, textured areas. Covers with a thinner nap hold less paint and are best for smooth surfaces. Avoid foam roller covers because they leave thousands of pits on your surface. Instead, use covers that have a fabric nap.
1/4” to 3/16” nap: A good nap for fine, mirror-smooth walls, ceilings, and doors
3/8” nap: Your standard, go-to roller cover for most interior surfaces
1/2” nap: For medium-rough interior surfaces, such as textured walls or ceilings
3/4” nap: Use for very rough surfaces, such as textured “cottage cheese” ceilings or concrete
