api 5000Api 6a Wn Flanges applications including pressure classes – 720 psi and 960 psi, the API specified no changes to the ASA B16.5 Standard, using the 300 lb. and 400 lb. flangesAPI Specification 6A covers wellhead and tree equipment as follows: API Specification 6A Wellhead Equipment Valves, Chokes, and Actuators Plugs, Connectors, and Gaskets Other