Rigid ducts and fittings connect to form duct runs that direct airflow in an HVAC system. Their construction is stiffer and more durable than flexible ducts. Clamp-together industrial ducts and fittings feature connection points and clamps with integrated seals that rapidly assemble and disassemble. Self-sealing ducts and fittings have built-in sealing gaskets rated to SMACNA class 3 leakage standards. They reduce the time and materials needed for installation. PVC ducts and fittings are lighter, more corrosion-resistant, and less conductive than metal ducts. Rigid duct accessories modify, repair, or improve the function of an HVAC duct.