I don't know what kind of racing requires it but here is what the description said

"Single-chamber perfomance for the track.

Flowmaster's patented Delta Flow technology was used to create the Delta Force One Chamber Race mufflers. These mufflers provide maximum scavenging, for added torque and horsepower in race applications where mufflers are required. This revolutionary technology has allowed Flowmaster to shrink case sizes for improved ground clearance. Flowmaster builds this series of mufflers by hand to ensure that they are the very best, in the most demanding environments. These are the mufflers to use when all that counts is winning!"

Who knows? I just like the way they sound!