Berk hfc are usually preferred around here. They have a 200 cel count I think, don't quote me lol any hfc will fit any exhaust due to all the parts are meant to fit with any part. Erz are pretty good but it really depends if you want rasp or not. Check out some videos on YouTube, that should help you get a better perspective on how loud the difference between the two should be. But as far as cel count I believe that the lower count the less restriction and therefore the louder the sound. Hopefully some of our fellow Z drivers can help you out. Good luck bud!
