ROLLER COVER 4" W/ 1/2" NAP. ROLLER COVER 4" W/ 1/2" NAP. This product is an ideal paint roller microfiber cover for smooth application surfaces and for all types of paints and stains. It is spill resistant and has a core that is also solvent resistant. It also provides 50% more coverage than covers made from other fabrics. Made in China, it also has an extra heavy duty core.