Speedi-Products SM-28A90 12 12-Inch 28-Gauge 90-Degree Round Adjustable Elbow 12-Inch Sheet Metal 28 Gauge adjustable elbows Used in HVAC round pipe and flexible Warm air duct systems For turns through 90 degrees and are simple to adjust Seal joints with approved duct mastic sealants Insulate Ductwork for improved energy efficiency and comfort