api 5000PO BOX 639 • Bakersfield, CA 93302 855-535-1555 phone • sales@ API FLANGE BOLT & RING CHART API Pressure Rating Flange Size & BoreApi 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. flanges