threaded flange

Slip-on Flange is essentially a ring that is placed over the pipe end, with the flange face extending from the end of the pipe by enough distance to apply a weld bead on the inside diameter.

Threaded flanges, also sometimes referred to as companion flanges / screw flanges / NPT flanges, contain a female NPT thread in the center for connection to male NPT threaded piping. Threaded flanges are common when creating reducing connections. Other thread styles are available for machining, aside from the standard NPT form as designated by the ASME B16.5 specification.