40 Delta Flow Stainless Steel – 2.50 Offset In / 2.50 Center Out – Aggressive Sound. This two chamber design incorporates Flowmaster’s Delta Flow technology. The Delta deflectors generate increased scavenging for better performance and reduced interior sound. Milder exterior tone and reduced interior resonance over standard 40 series. Constructed of 16 gauge 409S stainless steel and fully MIG welded for maximum durability.