These sanding discs work great. They work as well as the major brands and with this set, I got 100 pieces for less than a fraction of the price of just a few discs from the other brands. The discs attach securely to the sander with strong hoop and loop velcro. They will fit standard 5 inch orbital sanders with 8 holes. The sheets are 125mm in diameter and 0.2 inches thick. The set includes 20 discs of each grit from fine to coarse. The grits are 80, 120, 150, 180 and 240. The discs work on lots of different materials and won't clog easily. I like that I get a variety of grits so I always have the right sanding strenght for any projects.