Originally Posted by TarheelTerp
Like couplings, tees, elbows, toilet flanges, etc ?
Yes... they make them.
As to "O.D." reference I'll assume you made a typo.
Pipe is measured on the INSIDE.
Pipe is measured in both I.D. And O.D. why? I.D. for fittings O.D. for making block outs here is a good example say your doing new construction and you want to have the DWV got through the stem wall and you put a Thin wall PVC 4" ID pipe there the OD of that pipe is 4" 1/16th were as ABS OD is 4" 1/8th You just pooched yourself when you tear that block out, out. Your 4 inch ABS will not fit thru the stem wall.
So you better know both. Also When Pipe fitting you need to know the OD to find the take offs for long radius 90's and such. So No pipe is not just measured in I.D.