Mirka?s backup pads are manufactured using top quality molded polymer construction. Each pad is balanced to eliminate vibration and provide superior finishing. The medium density polyurethane foam is firm enough to level substrates, while conforming to minor surface contours. Pads have a maximum operating speed of 12,000 RPM. Regular and heavy-duty vinyl faces are available for use with PSA discs, and a grip face is available for discs using a hook-and-loop attachment method. The specially treated vinyl pad face offers excellent adhesion and ease of removal without paper delamination or tearing. The grip face has durable nylon hooks for use with fabric loop-backed disks.