Stainless flue

[Flabuck]

I was just looking at some of the photos in the gallery and I noticed that the stainless steel flues on the ovens look pretty hardcore.I am building an oven(my first)and I was just going to use some stainless vent pipe from Lowes.Is this OK or should I buy something more substantial?Keep in mind that mine will not be exposed,it will be in a stack.It wont see any weather.If I need to buy some where can I get it?Is there a good sight I can on to order some?I did notice the base plate for the flue looked like it was made for fireplaces and ovens.
Thanks guys!