9541 4in Ultra Flex Hook and Loop Backer Pad by Husqvarna 400304 Ultra flex 4″ Backer Pad 4″ Hook and Loop backer pad for attaching sand paper, or felt wheels. Diamant Boart’s exclusive backer is the answer for Ogee and Bowl Hole polishing. . Posted in Polishing & Profiling Equipment, Polishing Pads, Buffing Compounds, & Backer Pads, Tile & Stone Tools tagged with Husqvarna 400304