You may like this post. This is very useful chart that i would like to share with you.To get the updated chart , go to the original site at the end of this post. CARBON STEEL PIPE BUTT WELD FITTINGS NPT & SOCKET FITTINGS FLANGES A53 A234 WPB A105 A105 A106 GR. B A234 WPB A105 A105 A106 GR. C A234 WPC A105 A105 ALLOY STEEL PIPE BUTT WELD FITTINGS NPT & SOCKET FITTINGS FLANGES A335 P-11 A234 WP-11 A182 F-11 A182 F-11 A335 P-22 A234 WP-22 A182 F-22 A182 F-22 A335 P-5 A234 WP-5 A182 F-5 A182 F-5 A335 P-9 A234 WP-9 A182 F-9 A182 F-9 A335 P-91 A234 WP-91 A182 F-91 A182 F-91 LOW TEMPERATURE STEEL PIPE BUTT WELD FITTINGS NPT & SOCKET FITTINGS FLANGES A333 GR. 1 A420 WPL-6 A350 LF-2 A350 LF-2 A333 GR. 6 A420 WPL-6 A350 LF-2 A350 LF-2 A333 GR. ...