This specification2 describes seamless and welded nickel alloy tubing on which the external or internal surface, or both, has been modified by a cold forming process to produce an integral enhanced surface, for improved heat transfer. The tubes are used in surface condensers, evaporators, heat exchangers and similar heat transfer apparatus in unfinned end diameters up to and including 1 in. (25.4 mm).The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.