Mirka 23-321-400 Bulldog Gold 5-Inch 5-hole PSA Vacuum Disc 400 Grit is a 5-inch abrasive disc for sanders that use a pressure sensitive adhesive backing. This is a sanding disc designed for fine finishing and controlled stock removal on compatible 5-inch PSA vacuum sanders. Model Number: 23-321-400. If you need a finer grit disc that still cuts consistently and holds up through repeated passes, this is the kind of abrasive that makes sense.

The big story here is the 400 grit rating paired with Mirka's Bulldog Gold abrasive design. That combination makes it a good fit for refining a surface, evening out previous sanding marks, and getting material ready for finishing steps where a rough scratch pattern will show. It is not a coarse rip-down disc. It is for the stage where consistency matters and you want a more controlled result.

Mirka uses durable aluminum oxide grain, which is a proven abrasive for general sanding across wood, fillers, primers, and other common shop materials. The resin bonding supports the grain so the disc keeps cutting instead of falling off too quickly. In practical terms, that means less wasted paper and fewer disc changes when you are working through a box on repetitive prep work.

This Bulldog Gold disc also uses a semi-open coat and a stearate coating to help resist clogging and loading. That matters because loaded discs stop cutting cleanly, run hotter, and leave a less consistent finish. If you spend time sanding surfaces that can gum up abrasives, that anti-load design helps the disc stay useful longer and maintain a more even scratch pattern.

The 5-hole vacuum pattern is there for dust extraction when used with the right sanding setup. Better dust pull means cleaner sanding, less buildup on the disc face, and better visibility on the work. The pressure sensitive adhesive backing also makes setup straightforward. Stick it on, line up the holes, and get back to work without dealing with hook and loop wear or a loose fit on the pad.

For compatibility, this disc is intended for 5-inch PSA sanders and is listed as fitting tools such as the DeWalt DC421 and DC423, along with certain 5-inch Ryobi and Bosch 3107 and 3725 models. That is an important detail because PSA discs need the right pad style, not just the right diameter. If your sander uses a 5-inch PSA pad and a 5-hole vacuum pattern, this disc is built around that format.

This product comes packed 100 discs per box, which makes it a practical buy for shops and repeat users rather than someone looking for a handful of discs for one weekend project. If you do finish sanding regularly and want a known abrasive from a brand with a strong reputation in surface prep, this is a solid fit. It makes the most sense for users who care about a clean finish, repeatable cut, and less downtime from clogged discs.

Mirka 23-321-400 Bulldog Gold 5-Inch 5-hole PSA Vacuum Disc 400 Grit is a smart buy for finish work that needs consistency

This is the kind of abrasive you buy when you care more about a clean, repeatable finish than just chewing material off fast.

• Who it's for: Shops and serious users running compatible 5-inch PSA vacuum sanders for finish sanding and surface prep.
• Why it stands out: The aluminum oxide grain, resin bonding, and anti-load coating all work toward the same goal: a disc that keeps cutting clean and stays useful longer.
• Worth knowing: Make sure your sander uses PSA discs, not hook and loop, and check the 5-hole pattern before you order.

• What type of sander does this disc fit? It is designed for 5-inch sanders that use a PSA backing and a 5-hole vacuum pattern.
• What is the abrasive material? This disc uses aluminum oxide abrasive grain.
• Is this a fine or coarse sanding disc? With a 400 grit rating, it is on the fine side and is better suited for finishing and surface refinement than aggressive removal.
• Does this disc help reduce clogging? Yes. It uses a stearate coating that is intended to improve resistance to clogging and loading during sanding.