21 Inch Diameter Rotary Scrub Brush Fit for Emotor 500X Riding Floor Machine-Medium BrushOriginal Poly Brush for Emotor 500X and other scrubber machine with 21" rotary brush disc. It is a commerical contractor floor pad driver, which comes complete with riser and mounted clutchplate. It is easy to install. Fit most modern floor buffers scrubber machines. Measure the outside skirt of your buffer, and select a pad driver to match that measurement. Please check the design of the buckle, make sure the new one is as same as your old one.