Hiolit 5" 80 Grit Aluminum Oxide Non-Vacuum PSA Disc (50 Pieces) by Mirka Abrasives. Hiolit J is a flexible sanding material for metal and wood workshops. Compared to standard weight cloth products, Hiolit J is more aggressive, while still remaining very flexible. Hiolit J is a durable product with super edge wear, making it very suitable for tougher and more aggressive sanding of profiles and seams.