They are GMK keycaps, expect good quality, sound, and feel. Though be warned, if you don't wipe off your keycaps often, they might start shining earlier than normal, but they will shine either way, its just how the keycaps are. (also overused, but still a good keycap set)
After buying a dark red keyboard from another website I had to find a set of keycaps to match, and these almost perfectly fit my theme.
As other users have pointed out they do develop a slight shine as they wear out over time, though in my case it's only noticeable on the left Shift key where the edges remain unworn.