I weight about 125, and am 5'4", and wear a 34 a (maybe even a 34 aa)  The medium fits me just right, not too tight, and not too loose.  I would describe the support as light to medium, but then being small breasted I don't need much support.  These are very attractive sport bras, and look nice on me.  They wick well.  They have easily removable pads.  I have tried many sport bras and really think these are the very best.  I'm very happy with them and will be buying more in the future.