Less than 20 lb 20 Inches 14 Inches 6 Inches 0 50 10 max III Heavier than 2000 lb Heavier than 600 lb Less than 40 lb 28 Inches 20 Inches 8 Inches 0 50 10 max Note: Optimum gradation is 50 percent of the stone being above and 50 percent below the midsize. Reasonable visual tolerances will apply.