The 70 Series "Big Block II" uses a large case for increased volume and added sound reduction that will still fit many applications that our 50 series "Big Block/HD" muffler won't fit. It utilizes Flowmaster's patented "Delta Flow" technology for maximum efficiency and reduction of interior resonance. Use on high performance street cars, trucks, SUV's, RVs and tow vehicles. Constructed of 16 gauge aluminized steel and fully mig-welded for maximum durability.