The BR-2A is a nice chromic sturdy adapter mounts on the F mount on one face, and a 52mm on the other, so u can reverse mount say a 50mm onto it. Remember to reverse mount a lens with aperture ring so u can adjust the aperture!
the only catch is no metering, and when u step down to small apertures, it becomes very dim to shoot and lighting might be an issue. but still fun to use!
D200 and above does support metering for the older AI lenses which does not have a digital feedback via the coupling, so you still can meter, but you must pre-set the aperture value onto the camera manually in order for this to be effective.