Two identical rectangular heat-exchanger fin-arrays, with their bases in the same vertical plane, arranged in series one above the other, were used instead of a single array of double the original length fins to dissipate heat from a vertical rectangular base, which was kept at 40 degrees C above the ambient environment. The effect of the magnitude of the gap width between the two consecutive arrays, upon the steady-state rate of hear transfer from the heated base of the exchanger under natural-convection conditions, was investigated experimentally. When a gap width of 18 +/- 2 mm is used, a saving in fin material ensues together with a slight (similar to 3%) increase in the rate of heat dissipation, being achieved.