Outliner Brush Size 6 Series 838 Mack Brush Series 838 Size 6, Hair Length 1-9/16" The brush hair is Blue Squirrel and Black Ox Mixture, it has a Nickel Ferrule with a plain varnished wooden handle. The hair in the Out-liner Brush series 838 is very strong, but will not hold as much paint as the Mack Series 839 Out-liner. This outlining brush is great for outlining letters, for scroll work and applicable sign work. The Series 838 is suitable for most surfaces. Andrew Mack Brush Co. Out-liner Brush Size 6 Series 838 Lettering and Pinstriping.