DuraGRIT carbide products are graded by the US Standard Mesh size for each grit grain size, the same way ordinary sanding products are. The difference is as follows:
Carbide grains are sharper than the more rounded sandpaper grits and appear may more aggressive than an equivalent sandpaper product of the same grit number.
Also, as soon as you start using an ordinary sandpaper product, the grit starts wearing and degrading, grits break loose and backing paper tears. At the end of a large sanding project, you will be using a finer grit grade and will have an overall, uneven sanded finish when using sandpaper.
DuraGRIT carbide discs and blocks, do not degrade in the same way. Grit doesn't come loose and the steel backing doesn't tear.
At the end of a large sanding project, you will still be sanding with the same grit grade you started with and will have a consistent overall sanded finish to the job. To sand at a smoother grade, it is necessary to switch to a higher grit number.
Some users have indicated to us that when they discovered that their DuraDISCs lasted such a long time, they mounted their two favorite grit grade discs (e.g, 60 & 120 or 80 & 150) on two ROSanders and switched sanders, not discs.