My daughters both swear by these leggings! They are thick enough that they are not see through, they stay up and they are very comfortable. They are also very flattering!
They have the perfect amount of stretch without being see thru. I love them so much. I'd recommend them to everyone. I'm really small (5'1", 103lbs) and the XS fits perfectly.
I read about these on a fitness blogger's site when she recommended them as her favorite workout tights. I typically wear Lululemon but am always happy to find cheaper alternatives that are as good. I really like the fit and material and will buy this brand again.