I bought the CSI a few years ago when it was released. I wanted a matching stem for the k-wings and was willing to believe FSA that the CSI added stiffness to the OS-99, which is notoriously flexy. I have no experience with the OS-99, but the CSI version is still flexy. I could tell immediately, but at the time, everything was switching from 26.0 to 31.8. I was coming from a 26.0 Deda Newton and 215s, wanted the stiffness of the Newton, but also loved the k-wings. Unwilling to buy another 31.8 stem to replace the one I just bought, I kept it. Thus, my conclusion that the carbon wrap is just for bling.

I'm sorry to say it since you just bought the stem and a matching post. I hope you have a different experience.