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 as*Tolerances and ring gaskets are according to API 6A. Materials for API 6A Type 6B 5000 psi(34.5 MPa) Weld Neck RTJ Flange, API 6A 6B Weld Neck