RB is the model number for frames made to be sunglasses. RX are for frames that are meant to be prescription glasses. ... Pretty much all of Ray Ban's RX line is now made in China.
What do the numbers mean on Ray-Ban frames?
Most of Ray-Ban glasses have the size measurement printed inside the temples. The third figures in the sequence are expressed in millimeters and correspond to the following measures : diameter lens (example "52"), bridge width (example "18") and length of the temples (example "140").