This kit offers a means to balance the system at the outlets. This kit should only be used when the take-offs are difficult to reach. When possible, balance the system at the take-off (UPC-35-15). Placing the orifice at the take-off allows the sound attenuator duct to remove any noise caused by its restriction. For small rooms or when only a partial outlet is required, add a balancing orifice. Use balancing orifices sparingly to maximize the airflow. The Unico System® Outlet Balancing Orifice Package, Accessory Type: Accessory, For Use With: Plenum Take-Off