Mercer Type R Aluminum Oxide abrasive discs feature a 2-ply cloth construction. Aluminum Oxide discs are durable and long lasting providing twice the removal rate with a softer grind. Quick change discs (Roloc discs) offer a tool-free twist on and off system featuring a threaded male hub. Discs are used for grinding, blending, finishing and deburring on flat or contoured surfaces.