These are good tights.  I'm 53kg's and 161cm tall and got the small size. In hindsight I probably should have bought the XS as the small is quite high on my stomach (near my bellybutton) and this causes some rubbing by the tie.  It also bunches a little around the knee (I just wish i was taller and these would have been perfect!).  Great to run in, nice and firm around the hips and thighs. I stay in these for a few hours after 25klm runs and haven't had any stiffness or hip flexor problems (had a bad hip flexor injury that kept me from doing any running for 4 months). I would definitely recommend these tights.