220 Grit Open Mesh Sanding Screen, 4" wide, sold by the foot. Full rolls are 75 feet.
The open mesh allows sanding dust to pass through and not clog up the sand "paper". Good for sanding surfaces that create a lot dust, such as foam, surfboard blanks, spackle, plaster, etc.
For shaping the rails of surfboards the sanding screen softens with time and gets better the longer you use it.