3Mâ„¢ Hookitâ„¢ Microfinishing Film Disc 366L is rated Best in the 3M Microfinishing line of film backed discs. It features premium, micron-graded aluminum oxide abrasive bonded to a durable polyester film backing to produce a fast cut-rate and uniform finish on wood, solid surface composites, plastic, fiberglass, paint prep, coating and corrosion removal, primer, e-coat, or metal.