Back Up Pad for attaching Diamond Polishing Pads. The velcro back up pad finds a sweet spot between a superflex backup pad and a standard 4″ Flexible back up pad. The design of the velcro back up pad is the same design as traditional flexible velcro back up pads. However it is much much softer and more flexible. Sometimes you need just a little more flex when doing bowls or ogees. The velcro back up pad is just the ticket.