I just learned about these RX-inserts that apparently will fit M-Frames. They are marketed as fitting safety glass Brand called ESS and M-Frames. ESS is a brand used my military, Police, fire responders etc. I normally wear contact lenses but always prefer to wear my RX-Radar-Oakleys, sadly they are falling apart after 14-15 years. I am interested to hear if anyone has tried these RX inserts?