Hi there- There are really two questions here... The first is, do breast implant sizers accurately simulate a breast implant. The answer the that question is absolutely- this is so because the sizers (at least those I am familiar with and use) are basically implants that are a bit more durable so that they can be re-sterilized and re-used. They have the same dimensions for a given volume that the corresponding implant will have, and so when a sizer goes in, it does give a very accurate representation of what the same breast would look like with an implant of the same type and volume. The second question is whether the breast can be expected to look like it does in the OR with the sizer in after you have healed and achieved your final outcome. The answer to this one a bit more complicated. All breasts will go through a period of evolution after surgery, during which the shape changes and becomes more natural. This evolution is more pronounced in breast augmentation patients who have never been pregnant, because their skin and breast tissue have not been through the stretching and relaxation cycle that women with children have experienced. In other words, if you've never had a baby, the change your breasts undergo from the day after your breast augmentation to your final outcome ~3 months later will be a bit more significant. You should not fret about this, however, as this evolution in breast shape is almost always an improvement over this time. It is your surgeon's experience, skill, and most importantly, his/her experience that determines whether the appearance of your breasts in the OR with a given sizer in place approximates your goal or not. His/her understanding of what your skin and tissues are likely to do over time under the force of the implant of similar volume helps him/her make the decisions most likely to result in your satisfaction. So the bottom line is that sizers area a valuable tool, but as with any other tool, the person holding the tool is much more important. Choose your surgeon wisely and based on their education, training, experience, outcomes, personality, and reputation. www.DrArmandoSoto.com Here is a bit more you can read about choosing a surgeon: