3 inch (80mm) Twin wall flue Dinak DW. Twin wall flue system manufactured in Europe. Dinak DW is a class 1 Twin wall flue suitable for use with wood, coal, ...read more.
if you want to make a flue out of stainless steel look up folding over copper sheet to create a seal you want a double fold over to get a good seal on flue pipe
you can make it out of 1m or 2m thin sheet
otherwise buying flexi 3" stuff or buy wagon exhaust