For being considered "Slim Fit", I think this tank fell short. I was really excited to get it and when I opened the package I was really impressed with the material. Super soft and stretchy and was very comfortable on... the problem was how loose it was. I am 5'1", 108 lbs and ordered an XS. What a bummer when I put it on. The front was very baggy in the chest area (I'm an A cup) and was loose all the way around. I was hoping because of the Slim Fit labeling I'd be good to go. I don't have any other Reebok clothing so I had no idea going into this, but usually a universal Extra Small will fit. Needless to say I returned the tank and most likely won't be purchasing Reebok clothing again (unless it's in the children's section, I guess).
If you really want to get a slim fit, I'd say buy a size down unless you are super busty. Otherwise, this tank should be labeled "Loose Fit".