Wiktionary
n. The diameter of the inside of a tube, pipe or other object. Often abbreviated "ID".
Usage examples of "internal diameter".
It was average size, a cylinder of re-formed asteroid material fifty kilometres long and ten across, spinning to create about two-thirds of a gee at its internal diameter surface.
It had an internal diameter of two inches, external four inches, for the metal's thickness was one inch and it was of hardened steel.
It had an internal diameter of two inches, external four inches, for the metal’.
A section of steel tubing about an inch and a half internal diameter, one end was cut square and had a rubber sheath or hand-grip, and the other end was cut diagonally to a point.
Unless the end of the barrel is held steady, it'd take forever to drill out the internal diameter.
Outside the main facilities plant are open sheds which cover stacks of standard structural steel pipe, internal diameter 75 millimeters.