A top quality stainless steel, high temperature insulated twin wall Tee Cap, guaranteed for 10 years against defects due to faulty manufacture.   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.