Definetly go up a size! I'm a size 4/6 and ordered a medium to later have to exchange to a large. The material is really soft and silky, but super thin. There are small holes for breathability in the fabric. The cotton patch in the center is sewn a bit further back, but it is stitched nicely along the seam, which I don't know if others have this issue, but after some wear that piece of fabric starts getting loose for me. I wouldn't say you could wear these with leggings, you'd see the lines at lSee full review