Scotto1The fabric blend is unique to these socks, and it simply results in a fit that is more snug than the standard Fitsok. So, based on feedback from our members, we adjusted the sizing chart to reflect what people actually felt the socks were sized at. It should be noted that some people find these still a bit snug to put on, but once they're on they love the feel and there is absolutely zero slippage with no sense of restriction. Hope this helps and thanks for asking!