This DuraTech chimney flue pipe measures 6" length. Available in either a 5", 6" or 8" diameter. It's built with 430 alloy stainless steel inner wall, and stainless outer walls. The ThermaTech blanket insulation eliminates hot spots, with no shifting, settling, or voids. It features twist-lock design for safe and easy connection / disconnection without mechanical fasteners. No locking bands are required. Outer diameters are 2" larger than the inner. Allow 2" clearance to combustibles. DuraTech is tested and listed to the UL 103HT Standard for use with wood, oil, coal, and gas appliances. Need another size? Call us at 716-442-3004. (NOTE: Use the 6" DuraTech chimney pipe for our Chicago Brick Oven kits.) Limited lifetime warranty. Shipping is FREE in the contiguous US.