Not all "HP" tanks are the same. Faber makes two different High Pressure tanks, HP-100's and FX-100's. Most of the people here are referring to the FX-100's that are rated at 3442. The Faber HP-100 is rated at 3180+10% and is -7 lbs when EMPTY. The FX-100 is -0.57 lbs empty. Make sure you have the stats on whatever tanks you are buying.