In my practice I try to understand what the patient wants regarding size. For example, maybe she wears a B-cup now and would like to be a full C. By examining her and taking some measurments, I can decide if her desire is realistic and achievable. In the operating room, I use sizers to determine how many cc it will take to achieve her goal. That is the size implant I will use. Whether the breasts look "natural" depends on several factors including how tight the skin is preoperatively and if the patient has ever been larger before as with pregnancy or weight gain. Usually, with time, they all look natural.