For Nikon: 500 f/4 AF-S versions I & II, & VR, 200-400 f/4 AF-S VR I & II, 300 f2.8 VR I & II
Lowers the overall height of the 500mm lens by 1″ and the 200-400mm lenses by 0.1″.
The AP-554 has the advantage of greater clearance between the body of the lens and the foot, making it easier to use the foot as a handle for your lens. It is also longer, which facilitates balancing of lenses while using light-weight camera bodies as well as the heavier pro and prosumer Nikon camera bodies, even when using teleconverters.