The effects upon the performance of plate fin-tube cross flow heat exchangers due to outer surface geometry are considered. The finning parameter varying through 11 to 23, a total of ten geometrically distinct configurations were tested over a Reynolds number range from 100 to 30,000. The tube outside diameter with the collar thickness defines the characteristic dimension. The convective heat transfer coefficients are presented as plots of Colburn j-factor versus Reynolds number and compare well with previous studies. Typical data spread being +/- 10 percent range, the j-factor, the Reynolds number, and the finning parameter are correlated.