The aluminum backer’s arbor is 5/8-11 Female thread (NOT M14). 1 Piece of FREE GIFT 5 / 5 Inch aluminum Backer/Pad Holder. (5/8-11 Female Thread arbor). 28 Pieces of 5 / 5 Inch Diamond Polishing Pad for granite marble concrete stone. 5 Pieces X Grit 50 100 200 400. 2 Pieces X Grit 800 1500 3000 10000. 1 Piece of 5″ / 5 Inch (5/8″-11 Female Thread arbor). FREE GIFT aluminum Backer/Pad Holder. Recommend 3500 – 5000 rpm (griner or polisher speed must e lower than 5000 RPM). Wet or dry use (wet use recommended).