I just checked my pot and it's Stainless Aluminium Stainless sandwich on bottom. Why? I am not exactly sure, but I can tell you that I am going to ask my chemistry proffessor tomorrow and get some conclusive answers about what the benefits would be? I get the durability factor, but lets be honest is it really a factor. I am not playing tackle football with my brew pot, I am just brewing delicious beer. I have a feeling the melting points of these metal or alloys has something to do with it. Aluminium has a drastically lower melting point which leads me to thinking it may heat quicker or take initial heat faster than steel. I don't know I am just rambling at this point. Will get back with conclusive evidence from the Prof.