These keycaps are pad printed and are essentially crap. Mine had visible wear on printing after just a month of use. I get really OCD about this and it's just as annoying as typing on a shiny keycap set. Fortunately, TaiHao doubleshots can save the day at a low price, but whoever wrote this briefing should really chill out with the bold claims. These keycaps are a clear downgrade, and not a sidegrade, to PBT dyesub. It takes the great durability of PBT keycaps and ruins it with pad printed infill that looks terrible after a very short period of time.
ExpeditedIf I am not mistaken, I think the caps are laser engraved then infilled. I said infilled because the legends rise slight higher than the surface of the key caps. Laser etched (what Andrew said) is essentially "burning" the legends onto the key cap.
These infill can wear off quick. It happened to my Pure Pro.
At least, on the good side, the legends are printed toward the corner, so it may take a bit longer to wear them off.
But will the ABS DS caps able to replace all key caps on this particular board? I heard Leopold has some weird sizing on their space bar.
So, it is either buy this board, or wait till KBP V60 come out with MX Clear (and white) in July, according to their FB page. That board will be much easier to mod the caps.
bassBass, you would need to modify a standard space are to fit the stabilizers on the fc660m. There are ways to make it work without major reconstruction.