Selkirk 6″ Ultra-Temp Chimney 12″ Length The Ultra-Temp Chimney System is a rugged chimney designed for maximum safety and performance! Ultra-Temp includes a variety of components to meet every installation requirement. These components may be combined in a wide variety of ways to solve almost any chimney installation problem. Features: Material: 304-alloy stainless steel inner liner. Limited Lifetime Warranty. 6″, 7″, and 8″ List to UL 103HT. Stainless Steel Outer. 1″ Solid Pack insulation. Twist-Lock Coupler w/Locking Band included. 2″ Clearance to combustibles. UL Listed to UL 103HT. Specifications: Overall Dimensions: 12″ (L) x 6″ (W).