Nikon today announced the 600mm f/6.3 PF VR S lens, their second phase fresnel lens and their third lens that covers 600mm.
As with all phase fresnel lenses, this new lens is shorter in length and lighter in weight than you'd expect from the focal length and aperture specifications. 11" and just over 3 pounds, to be exact. Moreover, much of that weight is closer to the camera, making for a distinctly handholdable lens. Coupled with the Synchro VR Z8 and Z9 models, you get six stops (CIPA) worth of stabilization.
Since Nikon is emphasizing telephoto offerings at the moment, I have a separate article today trying to put all the puzzle pieces together for you.