Joest is Simply a Better Drywall Sanding Disc. Joest 9" Round Sanding Discs 15pk - Specially designed drywall sanding discs for use with the Porter Cable 7800 Drywall Sander. Perfect for dust free drywall sanding. Joest Abrasives drywall sanding discs produce the highest quality results. Here's Why: Perforation - Joest drywall sanding products have holes throughout the surface that allow the dust to easily escape, and Eliminate Load-up. Because you won't have dust particles clogging up your disc, you can now see the full potential abrasive life of the disc. Perforation allows the sheet to last longer and provide a higher level of finish. Dust is extracted through the perforations in a congestion-free-flow - not just at the edges of the sander, but over the entire surface! Fiber Backing - Joest abrasive drywall sanding sheets utilize a Non-Woven backing that draws the dust through the portholes evenly. Not only is the backing a nice additional cushion, but it drastically improves the performance and life of the sanding disc. Even distribution of sanded drywall material means you can Eliminate Sand Scratches! Aluminum Oxide Grit - Traditional drywall sandpaper uses sharp edged silicon carbide abrasive that starts out cutting hard, but doesn't wear evenly. Joest Drywall Sanding Discs utilize Aluminum Oxide grit that is rounded (instead of jagged), and wears uniformly. Joest products will cut at the same rate throughout their usable life, and will resist loading. 120 Grit, 9 inch discs, 15 discs per pack (Requires Joest useit Interface Pad).