Weiler steel wheel brush is measured using outside diameter (OD), with the OD being 6 7/8 in. The arbor attachment allows for easy mounting to the tool or pad. This Weiler part uses steel for the bristles which are 0.02 in diameter. All abrasive products that rotate or spin, such as the ones in this category, have a maximum speed at which you can run them. This Weiler wheel brush can be run at a maximum speed of 9000.