I just got a pair of these and it is so tough trying to figure out the sizing because all brands fit differently and the sizing is all over the map. I ordered this in 46.5. I have Giro Factors in 46.5 and Giro SLX in a 46.0, and Shimano R300's in 46.5. The Giros match the Shimano pair in sizing. The Fizik are a size bigger and significantly wider in the forefoot. I am toying with returning them for a 46.0 due to the big size.
It is not an awful fit and would allow for a larger sock, but my foot can move fore and aft making it a bad thing at times.