Insulated PipeStainless steel outer casing and inner liner. Double-wall pipe with solid pack insulation. Tested to withstand 2100 F. UL listed. This test helps to prevent product damage or structural hazard during brief periods of this excessive chimney temperature. Normal temperture is 1000 F. Pipe Data: Minimum clearance to combustibles - 2 IN. Stainless steel thickness: Inner lining and outer casing - .012 IN; couplers - .016 IN. Insulation density - 23 lb./cu. ft.No. 6ST-9: 9 IN long, 6 IN inside diameter, 8 IN outside diameterNo. 6ST-18: 16-3/4 IN long, 6 IN inside diameter, 8 IN outside diameterNo. 6ST-36: 35-5/16 IN long, 6 IN inside diameter, 8 IN outside diameterNo. 8ST-9: 9 IN long, 8 IN inside diameter, 10 IN outside diameterNo. 8ST-18: 16-3/4 IN long, 8 IN inside diameter, 10 IN outside diameterNo. 8ST-36: 35-5/16 IN long, 8 IN inside diameter, 10 IN outside diameter