United Abrasives- SAIT 57606 Closed Coat Aluminum Oxide 4-Inch x 21-Inch 1-AX 100 Grit Sanding Belt, 10-Pack 1A-X/2A-X: Aluminum Oxide, closed coat, X weight cotton. For general purpose sanding grinding and finishing of ferrous and non-ferrous metals, wood, cast iron, ordinary and alloyed steels and stainless steel.