I'm 5'10", size 20/22. The smallest size fitted very well. Room to spare but that didn't cause any problems or wrinkling. They were very comfortable and looked good. Better for me than the 50 denier smallest size which were very voluminous: they looked ok and stayed up but the legs did need heaving up from time to time and there was just so much "tight" everywhere.
I tested a sample pair of these tights - they were so so soft, super easy to get on and felt as if I didn't even have tights on! They weren't at all bulky, I really did feel cosy. The icing on the cake was not feeling the need to take them off as soon as I got home!