The Flowmaster 70 Series Big Block II Mufflers are specifically designed for large vehicles. For maximum volume and efficiency the Big Block II Flowmaster mufflers are designed around a large case. However, they are 2 inches smaller than the original Big Block Flowmaster muffler, allowing for a much easier installation process when working in tight areas. The Flowmaster 70 Series Big Block II mufflers also sports a special resonant tuning chamber, which makes the mufflers significantly quieter on the inside of the vehicle. Great for tow vehicles, RVs, and trucks with dual exhaust.