[RC-Monster Mike]

This is different than the "cast" parts, but similar in the fact that you need to make the mold before you can make the part. The parts are quite inexpensive to make AFTER you make the casting. Those extruded aluminum heatsinks are cheap enough AFTER you buy the extrusion head(couple thousand $$), but they are useful only for the motor size/diameter they are intended for. The Castle blower is universal in its fitment - "Fits on motors with outside diameters between 1 1/2" and 1 7/8". This universal utility would not be possible with aluminum(and pretty much "rules it out" for this particular item). I don't think any description of the item eludes to aluminum construction in any way - not sure how anyone would be "expecting" it based on the product description. :)