I'm 5'6", 21, 120 lbs girl. I'm thinking 375 cc or 400 cc but not decided yet. I'm too confused (Photo)

Although it is difficult to give a good recommendation without a physical examination, from the photos and your body dimensions, I would think either the 375cc or 400cc implant will get you a to a full C / small D size breast.  The size difference is only about 6%, but will actually be less after it is placed since you already have some breast tissue. However there are other factors to consider as well.  Such as breast width and what type of implant you want.  If you desire silicone implants, they are pre-made so you may not have too much of a choice.  All these factors can be discussed in a consultation so that your goals can be reviewed and a plan tailored specifically for you.With that said, most patients after their breast augmentation tend to say they wish they were a bit bigger rather than a bit smaller, so something to think about.Good luck and hope this information helps.  Feel free to reach out if you have any further questions.- Dr. Roger Tsai   

You should meet again and discuss with your plastic surgeon after doing the rice test.  I describe it in the attached video.  It will make you feel a lot more confident in the size you are choosing.