Armor BLK™ Aluminized Steel Axle-Back Exhaust System with Split Rear Exit by MBRP®. Exhaust System Type: Axle-Back. Exhaust Tubing Material: Aluminized Steel. Main Tubing Diameter: 2.5". Exhaust System Sound: Aggressive / Loud. The MBRP Armor BLK™ is all about style. It’s stealth black look takes any vehicle to the next level. The Armor BLK™ Series exhaust systems crank your vehicle’s style dial to 11. The Armor BLK™ series offers the same performance as the other series with an engineered, high-heat black powder coating on the tailpipe(s) and tip(s). Manufactured using heavy-gauge Aluminized Steel tubing throughout the whole system, everything but the tailpipe and tip are left as mill-finish steel for better resistance of damage under your vehicle.