This is labelled a Men's 6 (Woman's 5). I have size 5.5 feet so this feels maybe a half size larger, but it does leave room for different configurations of underlayers. Am completely satisfied. The MK100 is apparently an older now discontinued model, and can be found as new/old stock. I found mine, new, in box, at less than half the MSRP of a pair of new Quicklaces.