If I remember correctly mine were ground smooth inside the flanges. Mark even says they grind the welds smooth in the video they sent me. Sounds like there are definitely some Q/C problems. I'm sure you can see where I'm coming from on those collecters huh Nitrous. Imagine trying to tighten those things up while their on the truck with very little space between the frame on one side and the motor & tranny on the other. What was wrong with a traditional style collecter is what I want to know, and why do they continue to make them that way?