Used for both hand sanding and power sanding of contoured surfaces, these 1/2" thick sanding sponges are made from a soft, low-density foam with abrasive on one side and a grip backing on the other. The 18-piece set includes three each of 100x, 150x, 180x, 220x, 280x and 320x, at a saving of nearly 20% compared to buying the sponges individually.