Remind: The velcro backer/pad holder are with water feed hole, can be used for wet polishing. Rubber Backer’s max velocity / capacity is 5000 RPM. Please do not use them with high speed grinder or polisher. 3 pad holder’s arbor is 5/8-11 Female Thread. This package carries (a)-(c). (a) 160 Pieces of 4 / 100mm Diamond wet dry (Dry use recommended) Polishing Pad for granite marble quartz travertine stone concrete. 30 X Grit 50 100 200 400. 10 X Grit 800 1500 3000 Buff. (b) 1 Piece of 4″ aluminum velcro pad holder (5/8″-11 Female thread arbor). (c) 1 Piece of 4″ Rubber Velcro backer (5/8″-11 Female Thread arbor). Remind: Rubber velcro backer’s max velocity / capacity is 5000RPM, please don’t use it with high speed. (d) 1 Piece of 4″ VERY FLEXIBLE Rubber Velcro Pad Holder (5/8″-11 Female Thread arbor). 2.4mm pad thickness. Recommend 3500 – 5000 rpm (grinder or polisher speed must be lower than 5000 RPM). Wet or dry use (dry use recommended).