A top quality stainless steel, high temperature insulated twin wall flue pipe, guaranteed for 10 years against defects due to faulty manufacture. This stainless steel system consists of a 25mm high density insulated core surrounded by 316 grade inner liner is 0.5mm thick, (25% thicker than some products) and the 304 grade outer casing is 0.5mm thick. They are BSRIA approved to BS4543 Parts 2 & 3 and HETAS approved for solid fuel burning. It is supplied with a bright Annealed Mirror Finish.   PLEASE NOTE - We recommend a minimum of 1 metre vitreous flue pipe LINK is installed between the stove and stainless steel twin wall system.  Your vitreous flue pipe will either be 5" or 6" depending on which stove you have purchased.  Each stove product page has a link to which of the two stainless steel flue connectors you will require for your installation. All stainless steel twin wall flue systems are 6" (150mm) in diameter.