Most breasts aren't perfect orbs and they usually aren't identical. Be on the lookout for the way they hold in place as she moves around (especially her arms), and how they stay almost the same dimension -- instead of flattening out -- whether she reaches back or even stretches. Furthermore, when she bends over, you should see them fall if they're real.P.S. Guys, don't spend all your time trying to stare at women's chests this weekend k.
Watch out for women wearing a constrictive bra to make them come together. The overall shape will still not look right. With such a bra, you won't be able to notice the outer circles contouring the breasts.
On the topic of odd breast shapes, the top of her breasts are bubbled up -- just like bubble butts. Fake boobs defy gravity, so they might look like they're bubbling up. Natural breasts follow a more natural sliding curve line from top to bottom.