A stub-in is pipe into pipe. Use a reinforcement pad (repad) around the stub, where it meets the run pipe.
A coupling is a double female joint fitting. Threaded or socketweld, depending on everything.
A half coupling is a single female joint with a plain end, and is shorter.
Common...
Measure the circumference of the pipe with insulation in place. Do this with a string, flexible tape, or long piece of paper.
Use your algebra skills to solve for diameter (with insulation). Insulation is specified in standardly available thickness: 1", 1.5", 2", 2.5", etc. Keep in mind there...
