This genuine RUPES part is a replacement for the backing plate originally included with the RUPES BigFoot LK 900E Mille Polisher. The holes in the plate allow for proper airflow, protecting the polishing surface from overheating. Available in a 5" (125mm) plate designed to fit a 5.25"-5.5" pad, or available in a 6" (150mm) plate designed to fit a 6.25"-6.5" pad.