How To Choose The Right Paint Roller Brush By Size ? 12" to 18" -Used for painting extra large areas; i.e.. warehouse walls, ceilings, floors. The most economical time saver. ? 9" -The most widely used size in America today. Use for all general painting applications. ? 2"-2-1/2" For Trim, Rails, Molding: Medium Size Areas ? 7" -Used for painting smaller "enclosed areas" where fit does not allow a large size. ? 3" to 4" -Used for tight fitting spaces, trim and touch-up. 4" size especially used for isle marking. By Fill Material Natural Lambskin ? -Used best with solvent or alkyd paints. Excellent paint pick up and release. Polyester/Wool Blend ? -Contains the best properties of both materials. High ware resistance of polyester, will not mat down; better paint pick-up and release of wool. Used mostly by professional painters Polyester & Blended Fabrics ? -The most used fabrics on the market. These fabrics offer excellent ware resistance, better paint pick-up and release. Will not mat down.