Two runs of 1/2″ 3003 Aluminum tubing are run from the firewall up to the nose of the aircraft, and then covered in heat shrink tubing to add some insulation value to the line. At the aft end, the lines are installed with nuts and unions to a pre-made (by the factory) plate, and safety-wired. At the nose, we needed to install a 2-way valve so that we can select to heat either the fresh air oil cooler/cabin heater, or the recirculating air cooler/heater. An aluminum bracket was installed to hold the valve steady against the load of operating the valve, and stainless steel flexible tubing was run to and from each cooler/heater.