Coarse (30 micron or 750 grit) and Fine (9 micron or 1800 grit) sanding strips come in packs of 100 pieces in random widths (1mm-4mm).

If you are only going to buy one grit, in our experience, the coarse is much more useful and aggressive enough to finish casting surface textures, mold lines and seam lines. Also as the coarse wears down it becomes more like fine. The fine sanding strips are only useful if your surface is already smooth.