Bursten steel radial bristle brush is measured using outside diameter (OD), with the OD being 4 in, has a diameter of 4 in4 in and comes with a brush width of 3.95 in. The unthreaded stem attachment allows for easy mounting to the tool or pad. This Bursten part uses steel for the bristles which are 0.008 in diameter. The radial bristle brush has a length of 3.9 in. All abrasive products that rotate or spin, such as the ones in this category, have a maximum speed at which you can run them.