be drawn by the heat sink of this invention while it is only exemplary of this invention it is noted that in the form shown one fin body 12 covers substantially the entire area of the surface to which it is affixed while the other fin body 14 covers less than the entire area in order to allow for the contact area 15 0019 fig3 illustrates a practical embodiment of a product in which two heat sinks in accordance with this invention are employed the product includes a printed circuit board 16 on which are mounted semiconductor packages two of which not visible in fig3 are cooled by use of heat sinks 10 in accordance with this invention 0020 fig4 is a schematic illustration of a section through the circuit board 16 showing the engagement of the heat sink 10 with a semiconductor package 18 as will be noted there the presence of the fin body 14 enables enhanced use of a surface of the rectilinear body 11 which otherwise would have significantly lower heat transfer capability by guiding air flowing immediately adjacent the printed circuit board through the elongate tubes provided by the fin body additionally fin body 14 in forcing air to travel through its elongated tubes provides resistance to air flow.