Coatings are graded on a graphite hardness scale like pencils.
Think of it this way: on a graphite scale, 9H is the hardest form.
One easy method of evaluating scratch resistance of ceramic coating hardness is with a grading pencil test, which requires the use of a kit of pencils with assorted densities from H(softest) to 9H(hardest). Each pencil is used to make lines in the coating; the first pencil in order that does not scratch the coating determines hardness. Armor Shield’s base coat ceramic formula measures at 9H on the hardness scale; the highest possible scratch resistance currently offered in a nano-ceramic coating.