Quoted:
I am building a Flat top and have an F Marked Front sight base. I am looking for some Ideas on rear BUIS for it. I am not sure at this point if I want to go the flip up route or not yet so give me all the ideas you have. Most of the product descriptions I have seen don't say if they are for F height bases or not. Any info would be great.
I have two Troy rear flip up BUIS for my carbines with F type FSB (one was marked the other not marked but both are 0.040" taller) because sometimes I use a magnifier and higher power scopes.
The Troy are better in my opinion because of its solid feeling either raised or folded, no movement at all when being used, the windage adjustment are set in to prevent accidental mis-adjustment, and a low 0.460" folded height that would fit most scopes.
I would recommend the folding BUIS type so if you get a magnified optics later on you don't have to sell your fixed BUIS for a folding one.
If you want a military style BUIS take a look at the Matech, KAC, and ARMS, etc., the ones with the lower folded heights are the KAC and the ARMS model # 40L.
The Big Bad BUIS FAQ - tacked thread link