Rx-able means that these glasses frames can be fitted with prescription lenses. Some kinds of glasses in the optical stores cannot put prescription lense into them. Only these glasses that are marked with " Rx-able" can be replaced with prescription lenses. If you have vision problems and need to wear prescription glasses, these eyeglasses can meet your needs. After you have an eye exam to get your prescription, the optician will ask their lab technician to put prescription lenses into the glasses frames.
Before purchasing eyeglasses, we need to select frames. We need to choose a pair of eyeglasses frames that can hold a prescription. Lower quality eyeglasses frames are not designed to hold a prescription lens and are called non-Rxable. Rxable eyeglasses are eyeglasses frames that can accept a prescription lens. However, there are some sunglasses frames with an excessive wrap design can only accommodate prescription lenses up to a power of approximately +/-5.00 sphere. You can not put a prescription is sunglasses with a shield design. Some sunglasses manufacturer have facilities to make prescription lenses for their own frames, like Oakley, Bolle, and Maui Jim. Hope this helpful.
Rx can also be understand as prescription for eyeglasses lenses. The eyeglasses frames labelled as " Rx-able" means the glasses frames available for prescription lenses (also called RX lenses). With it, it can provide the eyes vision aids. And you can get that RX from an eye eye doctor after having eye examination. So, if you are poor vision and need vision aids, you must prepare well prescription for buying rx eyeglasses.