Eastern Sheet Metal Dual Wall Round Spiral Pipe and Fittings are available from 5" outside diameter to 84" outside diameter. Like our single wall offering our dual wall is avaiable with Eastern Tight and Eastern Flange connections and in the same side variety of materials. ESM can provide any combination of inner walls, perforated or solid, we prefer solid inner walls for fittings and perforated inner walls for spiral duct, along with several types of insulation. We can provide our standard fiberglass, ductliner or our own E-Free insulation with a polyester rayon facing to keep fiberglass out of the airstream.