The Mirka IRIDIUM 9" Grip 9H Styro sanding disc, Model 24-9CU-040, is a coarse abrasive disc built for fast material removal on polystyrene, textured walls, and ceilings. This is a sanding disc designed for leveling and shaping broad surfaces. If you are working exterior insulation systems, wall prep, or surface correction where speed matters more than fine finish, this is the kind of disc you reach for first.

What makes this disc matter is the combination of a large 9 inch working face and a coarse 40 grit cut. That gives you more surface coverage per pass and a faster bite into foam and similar materials. On big panels and overhead work, that means less time chasing uneven areas with a smaller abrasive and fewer passes to get a flat, workable surface.

The Grip backing is important because it is built for quick attachment and removal in the right sanding setup. That saves time when you are swapping worn discs on active jobs instead of fighting adhesive-backed consumables. The 9-hole pattern is also part of the system fit, so this is not just a generic round abrasive. It is aimed at the matching 225 mm platform where dust and debris control are part of the process.

Mirka positions the IRIDIUM Styro line as part of a system intended to eliminate debris when leveling polystyrene and textured walls and ceilings. In real use, that matters because foam and surface prep dust can get messy fast. Pairing the disc with the intended STYRO setup helps keep material moving away from the work area instead of loading up everything around you.

Material range is broader than polystyrene alone. Source data also lists plaster, filler, paint removal, primer, composites, plastics, veneer, hardwood, softwood, lacquer, chipboard, MDF, HDF, and several metals. Realistically, the coarse 40 grit version is best suited to aggressive shaping, stripping, and leveling tasks where you want fast removal, not a finish-ready surface. That makes it a practical choice for prep stages, not your last sanding step.

This Mirka IRIDIUM 9" Grip 9H Styro sanding disc makes the most sense for contractors handling insulation finishing systems, drywall and plaster prep, remodeling crews doing surface correction, and serious users already working in the Mirka STYRO setup. If your priority is fast stock removal across wide areas with a disc sized for the job, this is the right consumable. If you need fine finishing, step down to a finer grit instead of expecting a 40 grit disc to do two jobs.

Mirka IRIDIUM 9" Grip 9H Styro sanding disc for fast wall prep

This is the kind of abrasive that makes sense when you have a lot of surface to flatten and no patience for slow progress.

• Who it's for: Contractors and serious users working polystyrene, textured walls, ceilings, plaster, and other broad prep surfaces in a Mirka-style sanding setup.
• Why it stands out: The big 9 inch format, 9-hole pattern, and coarse 40 grit are aimed squarely at quick removal and system-based debris control.
• Worth knowing: This is a consumable for aggressive prep work, not a finish disc, and you need the right 225 mm Grip setup to use it correctly.

• What is this disc mainly used for? It is made for sanding and leveling, especially on polystyrene and textured walls and ceilings.
• What grit is this version? This part number is the 40 grit version, which is suited to aggressive stock removal and early-stage prep.
• What size sander does it fit? It is a 9 inch, 225 mm Grip disc with a 9-hole pattern, so it should be matched to that backing size and hole layout.
• Can it be used on materials beyond polystyrene? Yes. Source data also lists plaster, filler, paint, primer, plastics, wood products, composites, and several metals among its suitable materials.