api 5000*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 Neck5000# API Socket Weld Flange is made up of A105 carbon steel and has a minimum yield strength of 45000. API 10000 Flange is manufactured from hh steel alloy after heat treatment