In article unications,
Robert Bonomi wrote:
...snipped...
Plumbing stuff is specced by inside diameter.

O.D. is whatever the manufacturer feels like.

That may be true in the case of couplings or fittings that pipe screws
_into_ but the OD of the pipe itself is controlled by the spec, otherwise
pipe and fittings from different sources would not be interchangeable.
And unlike pipe, tubing is sized by OD.
--
When the game is over, the pawn and the king are returned to the same box.

Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar.org