The Internal 360° Hoops are mounted in sleeves on the inside of the ductwork creating a closed circuit around the circumference. This ensures an aesthetically pleasing duct that is kept open if the airflow is turned off. The hoops are removable for easy laundry. Internal 360° Hoops are available in duct systems from Ø155 mm [Ø6 in] and up. The hoops come pre-installed from the factory on ducts up to Ø660 mm [Ø26 in]. For diameters above Ø660 mm [Ø26 in], the suspension fiberglass rods are added on site. Adding the hoops is an easy process, as they simply glide in place.