I have three All American 921's, one was my Grandfather's, one my Father's, one I bought. I can inside and outside and never had the slightest problem. With their Pressure Regulator Weight, there is nothing to ever calibrate, as the weight can be set for 5lbs, 10lbs, or 15lbs. I don't think I've ever use anything other than 10lbs my whole life. These canners are Tanks.