Measure the diameter of the backing pad (the velcro/hook pad on your sander). Common sizes are 3" (75mm) for mini sanders, 5" (125mm) for mid-size, and 6" (150mm) for full-size professional ROS. The abrasive disc should match this diameter exactly. Don't measure the orbit stroke — that's different from disc size.

Generally no. The holes on the abrasive disc must align with the dust extraction holes on your sander's backing pad. Using a mismatched pattern will block airflow, drastically reducing dust collection efficiency and potentially causing overheating. In some cases, you can use a solid (no-hole) disc if you're working without dust extraction, but this is not recommended for extended use. Festool's 8+1 pattern is proprietary — standard 8-hole discs won't fit properly on Festool pads due to the center hole pin.

5-hole (common on Dynabrade, 3M): 5 evenly-spaced holes, good dust extraction for mid-size sanders. 8-hole (Bosch, Makita, DeWalt): 8 holes for improved airflow, better cooling and dust removal. Multi-hole mesh (Mirka Abranet, Festool Granat Net): Thousands of micro-holes across the entire disc surface, providing the best dust extraction and virtually clog-free sanding. Mesh discs are also more flexible and conform better to contours. The trade-off is they're typically more expensive.

Festool's 8+1 hole pattern (8 perimeter holes + 1 center locating hole) is proprietary. Standard 8-hole discs from other brands lack the center hole and won't seat properly on Festool pads because of the center alignment pin. However, Festool's newer multi-jetstream pads and mesh discs (Granat Net) follow more standard patterns. Some aftermarket brands like Mirka and Klingspor make Festool-compatible discs specifically labeled as such. Always check the packaging for "Fits Festool" or the 8+1 designation.

Hook & Loop (Velcro®-style) is the modern standard — quick change, reusable multiple times, and compatible with most ROS sanders. PSA (Pressure Sensitive Adhesive) discs stick directly to a smooth backing pad and are generally single-use. PSA provides a slightly firmer mount and can be cheaper per disc, but changing grits is slower. Most professional woodworkers and auto body shops prefer hook & loop. Match the backing type to your sander's pad — don't mix them.

ROS = Random Orbital Sander. Unlike a standard orbital sander (which moves in a fixed circular pattern), a ROS combines orbital rotation with random offset movement, eliminating swirl marks. ROS sanders exclusively use round discs (typically 3", 5", or 6") with dust extraction holes. If you have a square or rectangular sanding sheet, you're likely dealing with a finish sander or sheet sander — not a ROS. This tool is specifically designed for random orbital sanders and their round abrasive discs.

Some specialty sanders use non-standard patterns: 4-hole (some older Porter-Cable models), 7-hole (rare European designs), 9-hole (some pneumatic sanders), or 15-hole (large floor sanders). If your pattern isn't in our database, measure the hole circle diameter (the diameter of the imaginary circle the holes sit on) and count the holes. Search by your sander's specific model number or consult the manufacturer's manual. You can also consider using a universal mesh disc (like Mirka Abranet) which works with virtually any dust extraction pattern.