They advertise them as being made from old rail from the railroad. If so, it ain't cast iron cuz that stuffs made from steel. So maybe cast steel?? However, I have no problem with aluminum presses as in some Dillon presses, my RCBS ammomasters are aluminum framed and if they're strong enough to resize a 50 BMG, that strong enough for me. To answer the question on the Lee Classic series presses, they are as good as it gets. YMMV.