100% natural compressed dense wool felt aluminum backing plate - 5/8" - 13 threaded arbor Minimum operating speed 1,300 RPM 1/4" drill adapter Felt polishing wheel is 1.5" x 3" (1.5 inch (3.81 cm) by 3 inch (7.62 cm)) This polishing head is a 1.5" x 3" dense wool felt wheel with an aluminum backing plate to be along with cerium oxide to remove scratches in glass. With a 5/8"-13 threaded arbor and a 1/4" drill adapter (included) removing scratches from glass will be a breeze. If you can feel the scratch with your finger nail, it may be too large to remove with this method.