High compression. The top is made out of two layers: the one with structure and fit (that compresses very well) and the other layer is and over layer. This over layer tends to move up. I love the shape! Swimming in it is awesome! I have no worry of my bikini top deciding to show my boobs anymore :) Swimming is finaly a delight again. I am a size M and bought size M. It is a bit too tight, but I guess that's better with swimwear, because it tends to get wider anyways and now it does not flop of my body whenever I move fast. It's also nice to wear as a normal top.