Mirka MR-508 5-in. Pneumatic Finishing Sander with 8 mm Orbit (MR-508)

The Mirka MR-508 5 Inch Finishing Sander is a pneumatic palm-grip random orbital sander built for finishing work where you want more stock removal than a very tight orbit sander can give you. This is a finishing sander designed for surface prep and finish sanding on wood, filler, composites, and similar materials when a slightly more aggressive sanding action is useful. Model Number: MR-508.

The key number here is the 5/16 inch, or 8 mm, orbit. In real use, that means the tool cuts faster than a fine-orbit finish sander, so it is a good fit when you need to flatten, blend, or refine surfaces without stepping all the way up to a heavy material-removal sander. Combined with true 12,000 RPM performance, it is set up for productive sanding rather than slow polishing passes.

Mirka built this sander with precision molded composite components, and that matters for two reasons: durability and operator comfort. The composite body helps keep overall weight low while also reducing sound compared to a heavier all-metal build. On the job, that translates into a tool that is easier to control over long stretches and less tiring when you are working across large panels, doors, cabinet parts, or repair areas.

The low-profile design and palm-grip layout make the tool easy to keep flat on the work surface. That helps with control, especially during finishing passes where tipping the pad can leave swirl marks or uneven scratch patterns. Mirka also calls out a counter-balanced design matched to the backup pad size, along with premium counterweight bearings and moisture-resistant composite rotors. That is the kind of internal detail that supports smoother running and better long-term reliability in a shop environment.

Because this is an air-powered sander, it is a practical choice for users already set up with compressed air. At 90 psi and 16.8 CFM average air consumption, it is aimed at serious shop use rather than light occasional duty from a small compressor. Variable speed gives you another layer of control when you need to back down for more delicate finishing work or stay at full speed for faster surface prep.

Dust management is also part of the story. The Mirka MR-508 5 Inch Finishing Sander can be converted to vacuum operation with an external or self-generating vacuum adapter. If you are sanding filler, paint prep surfaces, wood panels, or composites, that option can make cleanup easier and help keep the abrasive cutting more consistently.

This sander makes the most sense for body shops, woodworking shops, finish carpenters, cabinet installers, marine repair techs, and serious DIY users who already run air tools and want a compact 5 inch random orbital sander with a more assertive finish-sanding orbit. If you need a tool for delicate final finish work only, you may want a smaller orbit. If you want a balance of finish quality and speed, this one is right in the sweet spot.

Mirka MR-508 5 Inch Finishing Sander for Fast, Controlled Finish Prep

This is a smart pick for air-tool users who want a compact random orbital sander that moves faster than a fine-orbit finish sander without getting clumsy.

• Who it’s for: Body shop techs, woodworkers, cabinet shops, marine repair pros, and serious DIY users with a solid air setup.
• Why it stands out: The 8 mm orbit and 12,000 RPM speed give it a useful mix of finish quality and material removal, and the low-profile composite body is easier on your hands over longer runs.
• Worth knowing: This is an air sander, so compressor capacity matters, and vacuum capability requires the proper adapter rather than coming built in as standard.

• Is this a pneumatic or electric sander? This is a pneumatic finishing sander that runs on compressed air.
• What is the orbit size? The orbit size is 5/16 inch, which is also listed as 8 mm.
• Can it be used with vacuum dust extraction? Yes. MR-Series sanders can be converted to vacuum operation with an external or self-generating vacuum adapter.
• What speed does it run at? It delivers true 12,000 RPM performance.