But Weld Fittings Carbon Steel : ASTM A234 GR WPB Stainless Steel (AUSTENITIC) : ASTM A403 GR WP304/L ASTM A403 GR WP316/L Schedule No / Wall Designation : SCH 10, SCH 40, SCH 80, SCH 160, STD 160, STD, XS, XXS Dimensional : ASME B16.9 / MSS SP-43 / MSS SP - 75