Pro Series™ Stainless Steel DPF-Back Exhaust System with Single Side Exit by MagnaFlow®. Exhaust System Type: DPF-Back. Exhaust Tubing Material: Stainless Steel. Main Tubing Diameter: 5". These entry level performance diesel systems feature 100% steel mufflers and mandrel-bent steel tubing. MagnaFlow systems give more horsepower and torque than factory exhaust systems by providing better exhaust scavenging and gas flow. They also provide the characteristic MagnaFlow looks and sound.