The 4 in. x 6 ft. Heavy Duty Semi-Rigid Aluminum Duct with Collars is ideal when all aluminum duct is required x code in some gas and electric dryer applications. It can also be used for bathroom fan venting. This duct is totally noncombustible and has a maximum operating temperature of 435°F.Aluminum collars on both ends of the duct swivel making for easy attachment to the dryer exhaust port and exterior exhaust hoodUL2158A listed and marked for safe dryer ventingNew manufacturing technology incorporated into the duct allows for easy rotation and therefore more durable handling of the duct by the contractorUL duct is thicker than the standard non-UL semi-rigid version that allows for a more robust installation