Pipes, Ducts and Stacks for Heating, Cooling and Ventilating Systems and Parts Therefor-Namely, Plenums, Elbows, Angles and Takeoffs; Trunk End Caps, Dampers, Starting Collars, Reducers, Increasers and Adapters; Stack and Register Adapters, Dampers, Boots and Heads; Furnace Pipe Drawbands, Flue Thimbles, Wedge Connectors, Casing Collars and T and Y Flues; Y Branches Perimeter Fittings; Ceiling Diffusers and Sleeve Insulation