I'm trying to order parts for my chimney but manards strange system will only send the double wall pipe to a store(I don't live within 500 miles of a manards). I can get all the class A stuff sent to my house(go figure). So that leads to the question of if I buy all the class a pipe from manards "including the stove pipe adapter" can I get the dbl wall stove pipe from another mfg I.E. duravent? This is for 8 inch pipe.