Joest grit particles have more rounded edges to help eliminate scratch marks. Grit rating is a measure of grain size not sharpness. For sanding drywall mud, sharp grit is bad!
2. They last much longer: The Joest sanding disc and foam pad have air passage ways which carry the drywall dust away from the sanding pad to keep the disc cleaner and cooler for longer life. High speed sanders tend to create heat which strips the glue and sand from the disc. Use only Joest sanding discs with the Joest foam pad. It is the only system which has air flow that carries the drywall dust from the sanding surface to the vacuum. To see more pictures of air flow click here
Joest Sanding Kit includes: 1 - Foam Pad 5, 25, or 50 - Hook and Loop Sanding Discs