Abstract: A calibrated flow metering tube insert consisting of an upstream and a downstream part to be installed in an existing metering tube of a larger diameter to reestablish the correct Beta Ratio range. The larger tube is removed from service and the insert installed and fixed in the proper position. Pipe nipples are placed through the existing orifice plate holder and connected to the insert at the differential pressure tap holes. This process allows the operator to utilize the larger, existing, primary orifice fitting or orifice flanges and his existing inventory of orifice plates, thereby eliminating the need to replace the complete metering tube.