Like Don said. Most pistons come with a recommendation for clearance that is safe but usually a little larger than ideal. This coating is applied to give only .001 clearance. To break it in, you apply a small load which scuffs off the coating where it’s tight as the piston expands. You then let it idle back down to let the piston cool. Oil can now get back in. Where the oil can get to the wear stops. You repeat this process increasing load and rpm each time. What you are left with is the ideal clearance and shape for your engine. Say you have to hone the block and now instead of .005 clearance you have .010. Instead of buying new pistons, you can have them coated with this stuff. Comes in handy when you have an expensive set of custom pistons. So you get get the ideal clearance, better ring seal and life, quieter, and less friction because the coating holds oil. Line2line is the only company that offers this type of coating. The other skirt coating out there only can be applied between .001 and .002 thick and eventually wears away. This stuff can be applied up to .020 and stays put.