Step 1: Real Boobs have a natural sag to them, they are fuller on the bottom then the top. If a breast keeps its perky roundness, there is an implant holding it up.
Step 2: Fake boobs or breast implants are very identical and look nearly perfect. Real boobs are not always perfect.
Step 3: If cleavage is rounded, and looks inflated, it's fake.
Step 4: If a skinny girl has DD breasts, they are fake, it does not happen naturally.
The measurement is done by measuring just below a girl's bust and then measuring around the largest part of the bust size where the nipples are. Subtract the two and each inch in size is a cup size in letters like A, B, C and so on. How do you tell just by looking at the boobs? A cup looks like lemons, B cup like the size of oranges, C cup like grapefruit, D cup like cantaloupe. If the boobs bounce when the girl walks around they are definitely C cup or higher.