Fuji Track / Fuji Track Pro / Fuji Track Classic

hmmm - whats the diff between fixed fixed and flip flop - i notice that the other side of the fuji hub has 2 different thread diameters - like this pic:
http://www.halorims.com/HaloNew/products/hubs/track/track-r-black-full.jpg
(not a halo hub, just looks the same)
is that fix fix or flip flop?

fixed/fixed means it's fixed both sides, flip-flop means you can put a sprocket on either side. If the other side has a stepped thread then you can put a fixed sprocket & lockring on it, otherwise, if it has no step in the thread, it will be a fixed/free flip-flop hub and you'll have to use a BMX-style freewheel