I have had a hard time finding leggings that weren't see through and uncomfortable.  I got a medium because I didn't want them to be too tight. I definitely could have got a small but I'm keeping the medium since I'm sure they'll shrink a bit in the first wash.  I'm definitely ordering some more as they're inexpensive and comfy.  They definitely have a lot of weight to them so you definitely don't have to worry about seeing anything through them.