6.2 ALLOYS FOR SPECIFIC APPLICATIONS The 6XXX series alloy range is by far the most commonly used in extrusion. Within this series there are a number of alloys which range widely in composition. extrudability and properties. There are in excess of fifty 6XXX series alloys (AA registered). However. there is a great deal of overlap between a number of these alloys [6] such that we need only discuss the most commonly extruded products: