BORLA exhaust is built of aircraft-quality austenitic stainless steel - stainless inside and out, not mild steel, not aluminum, not coated aluminum, not just wrapped with stainless on the outside for show. Coating techniques, such as aluminizing, can somewhat prolong the life of mild steel, but coatings suffer at the weld points. And, comparing aluminized steel to T-304 stainless steel is like comparing gold-plated metal to solid gold! T-304 stainless steel has the highest chromium content, making it the most resistant to corrosion and therefore the most desirable material for a long-lasting exhaust system. Note: Only the flanges are not stainless. In our twenty-year experience, we have found the 3/8--1/2 flanges are so thick they will never affect the performance or longevity of the system.
Best upgrade for my Sierra. I am very pleased with the quality and sound. I have received my part just in 4-5 days after I placed the order. Thanks Wes!