I played with one of my newly acquired C9's tonight. The first thing I noticed was that it felt just like a C10, maybe not as flexy and maybe lighter. The second thing I noticed was that I was getting a ton of racket head speed and consequently a ton of action on the ball. I began to swing harder on a vertical plane as my confidence increased. The balls began to break in a more pronounced fashion in the air. It was a Catch-22, but a good one. The guy I was hitting with said my balls had more bite and more pace. The C9 is about 20 grams lighter than the C10. I guess it's 20 grams lighter in the right spots, this one hit like a dream. I'm going to play a few more times with it, but if the trend continues, I may be setting the dials back to the C9.