The rubber backer is 5/8-11 thread (NOT M14). 1 Piece of FREE GIFT 5 / 5 Inch Rubber Backer/Pad Holder. (5/8 Female Thread arbor). Remind: Rubber Backer’s max capacity / velocity is 5000 RPM, please don’t use it with high speed grinder/polisher. 23 Pieces of 5 / 5 Inch Diamond Polishing Pad for granite marble concrete stone. 4 X Grit 50 100 200 400. 2 X Grit 800 1500 3000. 1 X Grit 10000. 1 Piece of 5″ / 5 Inch (5/8″-11 Female Thread arbor). FREE GIFT Rubber Backer/Pad Holder. Remind: Rubber Backer’s max velocity / capacity is 5000RPM, please don’t use it with high speed grinder/polisher. Recommend 3500 – 5000 rpm. Wet or dry use (wet use recommended).