7 Ultra Durable Diamond Polishing 13 Pad for concrete granite marble engineer stone glass. And 1 Piece of 7 Aluminum Pad Holder. Pad holder is 5/8-11 Thread, NOT M14 Thread. Remind: Backer’s max velocity is 5000 RPM. Please do not use it with high speed grinder / poliser. 13 Pieces of 7 Inch. Ultra Grade More Durable D iamond 3.2mm Thick Polishing Pad for granite concrete marble engineered stone and 1 piece of 7″ Aluminum Backer/Pad Holder (5/8″-11 thread arbor). 3 X Grit 50. 2 X Grit 100 200 400. 1 X Grit 800. 1 Piece of 7″ Aluminum Backer (5/8″ thread arbor). Remind: Please NEVER use high speed grinder polisher with rubber backer (Aluminum Backer’s max velocity is 5000RPM). 3.2mm thickness. Recommend 3500 – 5000 rpm (grinder or polisher speed must be lower than 5000 RPM). Wet or dry use (we recommend wet use).