Abbott Robinson Brushes Available with soft, standard stiff, and extra stiff bristles, our brushes come in three sizes: 9/16" (No 9), 11/16" (No 11), and 3/4" (No 12). Sold by the dozen. Classic, high quality natural mounted bristle brushes ideal for cleaning and polishing of denture acrylic, cleaning interproximal spaces after denture deflasking, and for general laboratory polishing applications. These well-known, industry-standard brushes also excel at applying polishing materials and at polishing of lab-processed composites, metal and ceramic crowns. Durable design features permanently attached bristles for improved performance and extended life without flairing. Available in Soft, Standard Stiff, and Extra Stiff bristles for use in all polishing, finishing and cleaning tasks. 25,000 Max RPM