This is a snap in perscription (or possibly non-perscription) lens adapter system for the HTC Vive that takes a common set of lenses you can order online cheaply from zenni.com. There is a frame piece that it held in with friction and then a lens portion that snaps to the frame using magents. This allows you to easily change out the perscription or remove the lenses entirely for those that don't need them. The frame portion acts as a scaffolding above the lenses to protect them if you don't have a lens installed.
You need both a lens and a frame piece printed out. Lenses obtained from a pair of perscription Zenni.com glasses and 6 magnets.
## Frame and Lens - THIS IS THE 43mm VERSION
There are now two different versions of the STL. There is a 40mm version and a 43mm version. All things being equal, I haven't really noticed a diffence between the 40mm or the 43mm version. If your IPD is on the high end, you may see some benefit from the 43mm version. The glasses from Zenni are the same price so it probably doesn't matter. You might as well use the larger 43mm lenses if you're unsure.
### 43mm Version
You need to order these frames/lenses from Zenni.com: mhttp://www.zennioptical.com/550021-metal-alloy-full-rim-frame-with-spring-hinges.html
They should be approximately 20-26$ US shipped. You can search around the internet to find coupon codes for free shipping or glare coating. I DEFINATELY recommend the glare coating.
You need to get the magnets to glue into the frame and the lens pieces. The magnets needed are 1/8" diameter and 1/16" thick model D21B-N52 and you need 6 total. I bought mine here: https://www.kjmagnetics.com/proddetail.asp?prod=D21B-N52
They are about 6$ shipped.
To assemble the kit, you need to first glue in the six magnets, 3 into the frame and 3 into the lens holder such that they will attract each other.
You can see a video here: https://youtu.be/Xb6jRee2Mpo
To install the entire kit into the Vive you need to expand the face piece to allow for the most room. Insert the bottom of the kit into the bottom of the Vive and push down on the spring loaded arms until you can slide the top pieces under the top of the Vive. Then you can contract the face piece of the Vive back down to hold it in place.
Here is a video describing the process: https://youtu.be/nh7g7V6I4us
Just for the sake of disclaimers, install and use these at your own risk. I'm not trying to get rich off this, just recoup some time spent and help fund my new printer.