If you choose our PRO Series Power Tank option it simply means you want our highest performance regulators. If you want even faster tire inflations AND the ability to inflate your nitrogen shocks then the PRO Series is for you. The main differences between the PRO Series over the COMP Series are that the regulator is designed for higher inlet and outlet pressures (4000 PSI inlet for N2 and 400 PSI outlet for shocks) and the gauges on the XP400i are liquid filled instead of dry to withstand longer bouts of vibration as in desert racing. Even if you don't need to air up N2 shocks the PRO Series is the highest performance CO2 regulator around and it comes with our Limited Lifetime Warranty.