Optimum Backing Plates are designed to work specifically with OPT 21mm Polisher. Additionally they are perforated to allow air to circulate through the Optimum Foam and Wool pads and through the polisher. This air movement will keep paint, pad, and polisher cooler which will improve the performance and the results. Additionally the lower temperatures will make your polisher and pads last longer and prevent paint from being damaged due to excessive heat and shear.