Real oakley sunglasses does not have the "o" from oakley stamped on the surface of the lens or have an autenticity label hanging from the nose bridge.
Always look for the numbers on the inner side of the leg, that's the code to identify real oakley sunglasses.
Look for the model and the "made in usa" on the inner side too.
Real oakleys always come with the microfiber bag and that bag always come with a label.
Don't let them fool you, always go for the real thing.