An EGR tube is a metal tube made of stainless steel, carbon steel, or cast iron that allows recycled exhaust gases to flow through it while on their way to the EGR cooler or EGR valve.
The EGR (exhaust gas recirculation) system is an emissions control system that takes some of the exhaust gases from your engine’s exhaust manifold and recirculates them back into the engine through the intake manifold. The exhaust gases are then pulled into the engine and combined with the fresh air and fuel entering the cylinders.
Recirculation of the exhaust gases in your engine helps to reduce combustion temperatures and improve fuel economy. The lower temperatures reduce the amount of Nitrogen oxides (NOx, a greenhouse gas regulated by the EPA)) produced by the engine. Automakers are required by federal law to limit the amount of NOx produced by their vehicles.