It is a glorified F2.
It has an all metal setting and it does have GB but only in all metal which I don't believe many ever used.
In disc the GB is at the same factory preset levels as the F2 despite what people were led to believe...often by several reps at Fisher that spread this misinformation for years.
Not worth the extra $200 for two features that hardly were ever used vs the F2 but discontinued now so no longer an issue and used ones are usually now sold for a much more fair and logical price.
Sorry about the rant but this was a big misstep in Fishers history in my opinion, a company I usually respect, it only was offered to fill a price gap between the F2 and the F5, IMO.
If only they charged less they wouldn't have come off looking so greedy.
They were so disorganized they never informed the reps about the GB thing or worse, even after repeated queries from owners of soon to be owners, they directed the reps to lie about it...I sincerely hope it was the former, not the latter.
Being in retail for almost 30 years when companies do things like this it just sticks in my craw, but they seemed to have behaved themselves since.
Be that as it may to answer your question on the F2 the 4" silly looking hockey puck concentric found me more silver and a shocking amount of gold than any other coil in the most trashiest sites imagined.
The 8" concentric was a good all around, could get to about 7-8" in decent soil and still had very good target separation.
The 10" concentric was dirt cheap at $ 59, heavier and pretty unwieldy unless you just scraped it along the top of the soil but you could gain maybe 2 more inches than the 8" in good soil conditions...I found its best use was to firm up and stabilize signals on the deeper ones and fringe targets.
Many reported that they bought large aftermarket DD coils for both the F2 and the F4 and got to the 10" level and a few up the the 12" or more area if they had the right dirt to accomplish this.
I never saw the sense in spending $200 on a coil for an entry level detector instead of putting that money toward a more powerful upgraded detector but many did and they said they found good coin targets fairly deep so they seemed happy with the purchase.
Others bought those bigger expensive coils and gained nothing so they eventually upgraded their detector.
What coil is best, for me it was the sniper but it all depends on what you hunt, where you hunt and how deep the targets were you are looking for...as always.