Product name 

5.5 inch flex sanding pad backer plate pad for Forced rotation Dual Action DA random orbital polisher set positive drive GA 

same good as Flex Replacement Backing Plate

The plate is designed specifically for flex polisher, and creates the forced rotation that sets the FLEX apart from other dual action buffers. 

Please kindly note the price is just for the 5.5" backing plate. not include the machine.