I love Smartwool socks. If you are reading this and you happen to be be someone who has never worn Smartwool and can't figure out why someone would pay $20 for a pair of socks, just try them. You won't be sorry. This was my first pair of Smartwool running socks. I bought both these (the Ultra Lights) and the Lights. Like all Smartwool PhD socks, they stay put on your foot and don't hold moisture. I have some other decent running socks but these are the best. No surprise there. I prefer these (the Ultra Lights) to the Lights. These are very thin which is how I prefer my running socks. The lights would be better for cold-weather running and runners who know they prefer more cushion would probably prefer them as well.