Gauges are factory calibrated to ensure accuracy. To determine the right gauge for your application, choose the Bourdon tube and process connection material according to the conditions and medium to which the gauge will be exposed. Then choose your desired range and accuracy. For added safety, the maximum continuous pressure applied to the gauge should not exceed 75% of the maximum pressure of the gauge. All gauges have a 1/4'' NPT(M) process connection. The 3'' gauges include a soft carrying case; order hard carrying case 68030-90 for 4.5'' and 6'' dial gauges.