These are Genuine Randolph Engineering Aviator II frames, made to the same exact standards as their military aviator sunglasses.
Each pair goes through over 200 separate operations during manufacture and uses a nickel-silver alloy for the frame itself.
If you want to know how tough these frames are, check out this video:
These are the exact same frames that are standard issue to U.S. military pilots.
You can work with your own optometrist to have your prescription lenses made and fitted into your choice of Randolph sunglass frames.
This listing is for one pair of Genuine Randolph Engineering 55mm Aviator II Prescription Sunglasses Frames.