These collars have a complete seal connection on one end. The volume damper is made out of 20 ga. galvanized steel with stiffening beads and a continuous 3/8” aluminum square shaft for strength and rigidity. Nylon end bearings are added to each end to reduce air leakage. All standoff collars have a 3/8” dial regulator elevated 2” for insulation.
Super Heto with 2” Standoff
Order as follows: A = Diameter