The maximum weights that the tire is designed to carry; dictated by the tire's construction. Metric passenger type tires are offered with a Standard Load Rating (up to 35 psi), or Extra Load Rating (up to 41 psi). LT Metric (truck type) tires are offered with ply ratings of C (8 ply), D (8 ply), and (10 ply) and at various inflation pressures up to 80 psi.