This 9 in. guard is required when using 9 in. type 27 grinding wheels on Milwaukee grinder (models 6080-20, 6081-20, 6082-20, 6086-20, 6088-20, 6089-20). It can be used with grinding wheels with either threaded or non-threaded hub wheels. When using wheels without the threaded hub you must use with hub adapter flange (43-34-0825) and disc nut (49-05-0051). Nylon washer 45-88-8466 is recommended to be used with threaded hub wheels to assist in removing wheels from spindle after hard use. No tools are needed to attach this guard to the listed grinders. The guard can be rotated around the spindle to achieve optimum protection for the operator.