Selkirk; Selkirk 6″ SuperPro Cathedral Ceiling Support Box; 77680 SuperPro by Selkirk has inner and outer walls of 304-alloy stainless steel. The mineral wool insulation is formulated to reduce the likelihood of corrosion. Components, such as flashings, have a coating which has twice the corrosion resistance of galvanized steel. Locking bands are recommended at each joint for extra security when cleaning and are required on all elbow joints, lengths between elbows, and where the horizontal section of pipe attaches to the tee. Outside diameters of SuperPro are 2 larger than inside diameters. 7 SuperVent Chimney The chimney’s inner liner and couplers are 304-alloy Outer wall is 430-alloy stainless steel, Limited Lifetime Warranty, UL Listed to 103HT Standard for wood, oil, coal, and gas. Most of the components for SuperVent chimney are the same as those for SuperPro factory-built chimney. The exceptions are the cathedral ceiling support box which does not have brass trim, the decorator ceiling support and black wall thimble which come with round trim collars with no brass trim, and the trim collar itself which measures 16 round and does not have brass trim. Includes: Support band and ceiling trim. Features: Material: 304-alloy. Limited Lifetime Warranty. Embossed twist-lock connections resist moisture penetration into insulation. 2 clearance to combustibles. UL Listed to 103HT Standard for wood, oil, coal, and gas. For 6 and 8 applications use SuperPro. For 7 application use SuperVent Chimney. Supports a total of 30′ of chimney (up to 15′ may be below the support). Specifications: Overall Dimensions: 6 (W) x 17 (H).