Make Model Spec C CLASS. 16 OPT IC CLASS. 16 OPT II.C CLASS. 17 OPTC CLASS. 17 OPT II.C CLASS. 18 OPT II. AMGC CLASS. 18 OPT III. AMGC CLASS. 18 OPT..C CLASS. AMG 17 OPT IC CLASS. BASE 15C CLASS. BASE 16C CLASS. BASE OPT II, 16 OPT III What should my pressure be?