Hey guys quick question. So the home I recently bought already has a thimble and chimney. Now I just purchased a Jotul f3cb. So now to buy the flue. The present chimney is 8 inch double wall. But I dont know how to tell if it is metalbestos or what the brand is. I was told that the different brands of flue/chim pipe cannot inter connect with each other. So what ever my chimney is I will have to buy the same brand flue. Is this true? if so how do I tell which brand my chim is? I dont see a stamped lable anywhere. also one more stupid question. an 8 inch pipe means the diameter of the INNER pipe is 8 inches right?