What differences are there between the G Sand Abrasives grades?

G Sand Discs are available in P1200, P1500, P2000 and P3000 grades – and as with all abrasives, the higher the number, the finer the scratch pattern. P1200, P1500 and P2000 discs are film-backed and are designed to be used dry on Medium and High Solids paint systems. P3000 discs however are foam-backed, are best used wet/with water and are especially appropriate for Ultra High Solids and Scratch Resistant Clearcoats.