Hi-Temp Woodburning Chimney, 2"" clearance to combustibles is required, unless noted differently, 12"" Pipe = 15"" Outside Diameter, Outer Shell = Galvanized Steel, Inner Shell = Stainless Steel, Only FMI Chimney is approved for use with FMI Fireplaces, Not approved for any other use, 2"" clearance to combustibles is required, unless noted differently, SKU: TWST5129