Inner Diameter 3 . Fuel Types Compatible With Wood/Oil/Coal, Gas, Pellet. UL Listed Yes. Length 16 . This DuraFlex SS 3 InchDuraflex Top Plate is the ultimate in flexible components for strength and flexibility. Use to seal top of masonry chimney and support the flex. Not for use with Ventinox flex. DuraFlex SS is the ultimate in flexible steel liners for strength and flexibility. It features 20% more stainless steel per foot compared to other liners on the market. Its extreme flexibility facilitates problem free installations where multiple offsets are needed. DuraFlex Pro is DuraFlex Pro is manufactured utilizing highly corrosion resistant 316 Stainless Steel. Listed to UL 1777 and ULC S635. 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.