Inner Diameter 7 . Material .006 Stainless Steel Continuous Weld. UL Listed. Attach to bottom of liner in the smoke chamber of a fire place, then pull up to form a seal between the liner and clay tile. Ventinox components are made from either 316SS VFT or superferritic stainless steel VG . Components feature an integral locking band, avoiding the use of pop rivets. Liners and components provide a penetration free top to bottom connection. When venting solid fuel heaters, Ventinox VFT must be insulated with either TherMix or ProFoil blankets to meet UL 1777 requirements. For all other applications, insulation is highly recommended for increased efficiency and draft performance. Looking for Simpson Dura-Vent? You found it! Simpson Dura-Vent has changed their name to DuraVent. DuraVent is a recognized technological leader in the venting industry. Consistently the first to market with new innovations in venting systems, DuraVent has captured a leadership position in emerging markets. DuraVent has patents for several products and continues to design safe and technologically advanced venting. The company's research into solving problems with corrosion, when biofuels such as corn are used, led to the break-through patent for PelletVent Pro. Scientifically proven materials and unequalled engineering make DuraVent products not only the best choice, or safest choice, but the only choice for professional quality venting products.