While these are excellent sanding sponges for freehand use, they also have a grip backing that allows them to be mounted on the hook facing of a 3" × 4" Mirka orbital sander platen or Mirka hand-sanding pad.
Suitable for use on softwoods and on curved surfaces, the sponges have a 1/2" (12mm) thick backing made of low-density polyurethane foam. The pliable, durable foam conforms to pronounced contours to maintain even contact with the work while cushioning your fingertips so the sponges are comfortable to use for long periods.
They come in nine grits from 36x to 320x. Made in Finland.