I ride long and hard. I demand the same performance from my cycling gear as I expect from myself. Castelli has been my preferred manufacturer for technical cycling apparel for more than 20 years. They fit, and perform, with style, pretty much as described with few exceptions. It took me a while to negotiate the "SIZING" charts, but I did. These are the first socks I've ordered from Castelli. Like their other clothing items, the socks fit small, and I may go with their xl size next time to compare fit. Although tight, I have no complaints. They are comfortable, and wick well without bunching, or creating "hot spots" while going "Full Gas", or on those recovey days.
I did notice a little freying of the weave after my last ride. This is concerning and I will be watching how long they last before a hole develops.