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, whilst extending between 75-350mm. They are BSRIA approved to BS EN 1856 Parts 1 & 2 and HETAS approved for solid fuel burning. It is supplied with a bright Annealed Mirror Finish. The Extension Length comes complete with a special locking band and provides an extension of 75mm to 350mm when slipped over a standard length. This can be used fully with any length starting from 500mm. When used on a 300mm length the minimum extension achieved would be 260mm. Sold fully insulated.