A couple things about the Simms G4 boot:
1) They're HUGE. Much wider size for size than other boots. If you look at pics of them you can see that the tread is way wider than the part your foot goes into. This makes them a tough fit in my Force Fins (float tube model) although they do fit.
2) For some reason without looking at the sole, it's almost impossible to tell the right boot from the left one.