I am 5'8 125lbs . very small 34 A . flat chested . what size is 325cc?

The best cosmetic result in any particular breast augmentation patient depends on a variety of factors, including: your individual anatomy, realistic expectations, a thorough discussion with the plastic surgeon about the options, and an understanding of the pros and cons of any particular implant choice. Proper sizing is not just about the number of cc’s. The thickness of your tissue, breast dimensions which include the width, height, and projection, as well as chest wall width all need to be considered when choosing an implant. Trying on implant “sizers” of various shapes and volumes while wearing a tight t-shirt, bra, or bathing sit at a preoperative visit will help you and your surgeon choose the optimal implant.There are no manufacturers' standards for cup sizing in the bra industry. The cups of a 32 C and a 38 C are significantly different. Cup size varies from manufacturer to manufacturer and even within styles from any particular manufacturer.Keep in mind that following the advice from a surgeon on this or any other website who proposes to tell you exactly what to do without examining you, physically feeling the tissue, assessing your desired outcome, taking a full medical history, and discussing the pros and cons of each operative procedure would not be in your best interest. I would suggest youdiscuss this with your plastic surgeon who should be certified by the American Board of Plastic Surgery and ideally a member of the American Society for Aesthetic Plastic Surgery (ASAPS) that you trust and are comfortable with. You should discuss your concerns with that surgeon in person. Robert Singer, MD FACSLa Jolla, California

Discussing your goals (or evaluating the outcome of) for breast augmentation surgery in reference to specific cup sizes is NOT a good idea and can be a source of miscommunication. 
Generally speaking, the best online advice I can give to ladies who are considering breast augmentation surgery ( regarding breast implant size/profile selection) is:

1. Concentrate on choosing your plastic surgeon carefully.  Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you're looking for. Ask to see lots of examples of his/her work.
2. Have a full discussion and communication regarding your desired goals  with your plastic surgeon. This communication will be critical in determining  breast implant size/type/profile will most likely help achieve your goals. 
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. I have found that the use of words such as   “natural”  or “C or D cup”  etc means different things to different people and therefore prove unhelpful.
 Also, as you know, cup size varies depending on him who makes the bra; therefore, discussing desired cup  size may also be inaccurate. The use of computer imaging may be helpful during this communication process.

3.  Once you feel you have communicated your goals clearly,  allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals.  Again, in my practice, this decision is usually made during surgery.
I hope this (and the attached link) help.