Subaru BRZ 2013-2017, DT-S™ 304 SS Cat-Back Exhaust System by ARK Performance®. Exhaust Type: Cat-Back. Exhaust Tubing Material: 304 SS. Main Tubing Diameter: 2.5″. With the many varieties of exhausts that ARK has to offer, the DT-Series premium exhaust provides the perfect combination of sound, style, and performance. The ARK DT-S premium exhaust has been carefully engineered and manufactured to ensure 100% satisfaction. With T304 Stainless steel, quality mandrel bends, and flawless welds, the quality of the DT-S exhaust is unrivaled.