I too have the Shuttle Chef and love it. From what I remember at the time of purchase there are two types of insulation on the outer pot the foam type stuff with plastic or stainless walls or the shuttle chef thermos brand that uses vacuum like in a conventional Thermos. It has heavy bases on both the 4.5 and the smaller saucepan.
I use mine occasional for meals at home ( does a great pot roast or silverside ) but I use it weekly to take a meal for my husband and I when my son goes to Air Force cadets ( 60km drive then 4 hour wait ) we take all sorts of things from soups and stews/curries to hot dogs and nachos, last night it kept pies hot for us. I have the 4.5 with the inner pot and also the bain marie, also have the carry bag and cutting board, I think I got it on a mothers day special and got about $70 worth of stuff for free.
It has been the perfect thing for this use, we have saved a fortune as at first we were going out to dinner every time we dropped him off so over the 2 or so years we have had some wonderful meals and found some great locations to eat them in.