These are my personal favorite leggings; I wear a pair almost every day. They are very stretchy and comfortable, great for lounging around or exercising, either way. I've worn them doing yoga myself, and they allow for full range of motion without binding at any seams. I am a larger-bootied lady and I do fit into the "one size", though I must admit in some of my pairs I've ended up with some holes near the threads eventually. It's worth it though, and other than that they've lasted forever. Those holes are the only reason I've ever had to get rid of a pair, so if you're any amount less bootiliscious than me you'll have these for years to come. 

This is a sample pair I had sublimated (printed) with a "branch" tattoo design. My idea with this is that you can wear them under a skirt or shorts and give the effect of having a tattoo on the side of your leg, perfect for Halloween or other costuming.