The Alumavent 4100 Series low leakage, standard performance control damper is specially engineered with a rugged one-piece frame that locks together without bolts, screws and rivets that can vibrate loose. Triple-vee blade design provides maximum strength. With its non-corrosive bearings, lock together frame and shake proof concealed linkage the 4100 series is very low maintenance and is an excellent choice for use in most low-leakage, low to medium velocity and pressure commercial applications.