which front sight base with A2 upper??

[cmath0100]

This has probably been discussed a lot here, but I thought i would ask anyways. My rifle I have on order has an A2 midlength upper. But I am not quite sure if it needs an F-marked FSB, or a standard FSB? Or if it even matters at all?

[bgoodman]

standard is necessary for the a2 upper

[cmath0100]

thanks!!