api 5000API 5000, 10000 are used in reference to wellhead 'christmas tree' pressure ratings as well used for the wing valve, master valve ratings. There may be hher classes asApi 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