R6 insulated flexible duct 8 inches inner diameter by 25 feet long Wide Application 8 Inch Insulated duct R6 ,has a wide range of applications in commercial and residential HVAC systems. The insulation provides thermal resistance, which helps to reduce heat transfer and improve energy efficiency. Air conditioning systems 8 Inch R6 insulated Flexible ducting are commonly used in air conditioning systems to transport cool air from the air conditioning unit to different parts of a building. The insulation helps to prevent heat gain and keep the cool air at a consistent temperature. Air conditioning systems 8 Inch R6 insulated Flexible ducting are commonly used in air conditioning systems to transport cool air from the air conditioning unit to different parts of a building. The insulation helps to prevent heat gain and keep the cool air at a consistent temperature.