Rate of flow is necessary in determining a filter's corrected differential pressure in a fuel system as required by the A4A-103, the U.S. Airline Fueling Standard. The design of the Gammon FR Meter is based upon the reliable Gammon Gauge and developed with ClaVal to mount to tubing present on a ClaVal "slug" valve. If no "slug" valve is present, Gammon can provide a simple orifice plate to serve the same function.