Well, I finished putting in the hybrid stage 3 clutch. It's not on Spec's web site, but it's a combination of materials. Carbon on one side like a Stage 3, and kevlar on the other like a Stage 2. I haven't beaten on it yet, since I'm still breaking it in. There is no chatter at all. I was warned about the Stage 3 chattering for a while, which was why I went with the hybrid. This clutch is smooth and they rate it at 600, vs. 680 for the Stage 3. We'll see how it holds up. If you want the part number, it's SC423H.