Anti-reversion?
 

Before the flaming begins (you get what you pay for, Save your money and go with a known brand, I wouldn't trust it, etc), I am curious about the design of these test pipes. They have an anti-reversion chamber in it. I have never heard of anti-reversion and was wondering how this possibly effects the sound of the exhaust as well as performance. If anyone has any knowledge of what the design concept is suppose to do and can further explain it more than "smooth out the exhaust" and "keep exhaust gasses from going back up the pipe" I would like to hear it as I am curious. Might get them just to see out of plain curiosity, but still REALLY skeptical to even entertain it.

Saw those on Facebook. I was curious as well

"Anti-Reversion chambers" sounds (and looks) like ad-speak for "tuned expansion chambers" to me - but I'm no expert.

Basically there is a cone (funnel) in the pipe. The large end is facing the engine. Think of the exhaust as a sound wave that is traveling down the pipe. As the sound wave comes to a muffler or something else. It sets up a sound wave that is traveling back to the engine (your reversion). If the wave can go back to the engine. It robs power by slowing down the exhaust. The cone stops the wave from traveling any farther in the exhaust towards the engine. Closer to the head, better the results. I've had a set of headers that had the cones just inside the header flange at the engine. I couldn't tell the difference with them.

So if it prevents the exhaust from going back up, would it possibly reduce/prevent the hiss that can be heard from other test pipes?

Don't know. The hiss is from the harmonics in the exhaust from the VVEL.