Yup, center-stemmed.
I didn't like this set on my Filco though to be honest, which is what I had bought it for. The keys I think are too thick - it totally changed the entire feel of the board, and the sound as well. Not only that, but the space bar just didn't want to play nice, it just kept sticking. I guess I could play around with it a bit more and add o-rings or something, but the set now happily resides on my Poker II.