Stub finishes are used with lap joint flange. In such a flange, the stub is butt welded towards the pipe, While flange is freely moved over the stub finish. It is essentially flange part but lined below ASME B16.9 which is why it can be regarded as pipe fittings. A http://valvesandfittings02345.bluxeblog.com/17451981/how-much-you-need-to-expect-you-ll-pay-for-a-good-valves-and-fittings