ASME SA179 KL Type Finned Tube With AL1060 Fins For Economizer and Air Heater An ASTM A179 KL Type Finned Tube With AL1060 Fins is a carbon steel core tube (ASTM A179) that has been mechanically altered to have a knurled, footed "KL" fin design, onto which aluminum fins (made from alloy AL1060) are embedded. Its primary purpose is to efficiently transfer heat in applications like economizers, air heaters, and other heat recovery systems. Here are some detailed breakdowns: 1.