These are certainly the best no-show socks I've ever had (and that includes Smartwool and even Patagonia). The fabric and fit are perfect and they are standing up well to the rigors of my heavy hiking use. I'm not sure how tolerant they are of relentless washing but I am keeping my fingers crossed. There's no need for specific left & right socks. Each of the three pair I have fit perfectly on my feet. Now let's talk about that fit. I wear a 9.5 shoe. I decided to size up to a large and I am lucky that I did. The only "criticism" I have is the fact that they do run slightly small, or at least the socks I have do. I went for the socks with as little cushioning as possible. If I need cushioning I will achieve it with my shoes, not my socks. In any case, I cannot comment on the more cushioned versions of these socks. Accept no substitutes, these Swiftwick socks are perfect no-show, lightweight designs. Just buy 'em!