When Jim Austin at New England Arms initially imported the FAIRs, only OU's were available. The standard configuration was round knob/SST/vent rib. However, straight grip/DT/solid rib were available as options.

When NEA went out of business, Cabela's acquired the FAIR OU's and sold them at very attractive prices. Nice guns. The consensus seems to be that the B. Rizzinis are maybe a notch higher in quality. I'm sure others here who've owned both could comment.