Pace Technologies, SIC-2110-400, 400 Grit SiC Abrasive Grinding Paper (Plain Backed)Bonded or coated abrasive papers of SiC are designed so that the abrasive will have a large number of cutting points (negative abrasive rank angle). This is achieved by aligning the abrasive particles approximately normal to the backing. Note that coated abrasives are not quite coplanar, thus SiC papers produce the maximum efficiency (cut rate, stock removal and minimal damage) because new abrasive is exposed as the old abrasive breaks down.Plain-backed papers are the least expensive, however, they require either a double sided adhesive or a paper holding ring. The disadvantage to using a paper holding ring is that the mounted specimen cannot track over the edge of the grinding paper. Thus the paper does not break down uniformly and thus can produce over grinding of the mount away from the sample. This artifact results in the polished mount exhibiting a crescent moon which can affect the edge of the specimen. This artifact has also been known as "mooning" or MRD (material removal differential).For metallographic abrasives the particle size is typically classified by grit size or average particle size in microns. Grit size would refer to the size of the particle if it were classified or sized with mesh screens. Roughly speaking, grit size represents the number of wires or mesh of wires per a specified area. Thus larger grits numbers would represent smaller or more openings in a mesh screen and thus would correlate to smaller sized particles. For example, a 120 grit particle is approximately 105 microns in size, whereas, a 1200 grit particle has a particle size of 2.5 microns. The difference between the European P-grading system (number has a P in front of the number) and the more common ANSI or CAMI standard is that the European number is based on the number of openings if the width of the wire mesh was eliminated from the calculation. Therefore for larger particles the P-grading is approximately the same as the ANSI or CAMI number (e.g. 120 grit = P120 grit), whereas, for finer particles the P-grading number can be much larger (e.g. 1200 grit = P4000 grit)Unit of MeasurePack of 100 pcs.