always used together with lap joint flange. Stub End are made from material compatible with the designed piping system, back up flanges do not have to be made from the same material. The flange can be made from less expensive material because it never comes in contact with the process fluid.
Stub End are typically manufactured by two methods. Type A & B Stub Ends are made similar to forged fittings such as Elbows and Flanges. Type C Stub Ends are made by forming pipe to the desired dimensions. Stub Ends are available in two standard lengths, MSS and ANSI.