... 5.Certificate:API,ISO,CE,eg astm a105n carbon steel weld neck flange size 1/2" to 24" ASME B16.5 24 ... ,F316L,F321,F347,F310F44F51,A276 S31803, A182, F43,Etc)Alloy steel(ASTM A694 F42,F46,F52,F56,F60,F65,F70, A182 ... , etcSpecial design available as the requirement of customer Slip On Flange Blind FlangeWelding Neck Flange ISO certificate steel flange(supplier)