I use these for ballet class and they're great, absolutely no chance of being see-through. The material wicks sweat as advertised. I'm 5'6", 135 lbs and I bought a L - fits around the hips and waist but bunches a little once I get dancing so I'll probably just buy the 2.5" inseam version in the future, especially since it comes in better colors. If you're my size and really want the 4" inseam, size M might work better. Great, sturdy shorts for dance class!
I looked for a long time on a couple different websites for longer length shorts, but every one I looked at had reviews that said they were see-through or not well made. I was getting discouraged when I came across these. I had no reviews to go on, but I took a leap of faith, and I am so glad I did! These shorts are comfortable, thick enough to NOT be see-through, and durable. They don't ride up very badly, and even when they ride up, there is never a danger of showing anything. I'm 5'6" and about 145 pounds and I got a Large. They fit great! Love, love, love these shorts! I'll probably buy more!