If you paid $10 from a shop or street vendor you know they are fake.

Real glasses cost money, so a bargain is a fake.

Buy from licensed stores where you have recourse if something is not right.

Countries that are to be looked for are MALAYSIA, THAILAND.

First Check: 'RB' will be etched on left lens towards hinge...AGAIN towards hinge and its thickness will be very thin as its a laser etching. If not its a SURE FAKE

Second Check: 'Rayban' will be printed on right lens towards top of frame so as not to obstruct vision. If not its a SURE FAKE

Third Check: On inside right temple (the part of frame that goes over ear), 'Rayban Made in Italy CE' will be printed. If not its a SURE FAKE.

Fourth Check: On inside left temple, Model number, name, lens color, frame size & lens size will be printed parallel. For eg. for model RB3190 with Gunmetal frame & green lens, it will 'RB3190 FLIGHT 004 58x18'