This Wimberley Replacement Foot for Nikon 400mm f2.8 and 600mm f/4.0 AF-S takes the place of the tripod collar foot and converts the collar to Arca-style clamp capability without the need for additional quick release plates. Critical mass is reduced & the profile of the lens is lowered, which makes it well suited to use with the Wimberley Sidekick. Every adapter plate is complete with both 3/8"-16 & 1/4"-20 holes to directly attach the lens directly to a monopod or tripod (without an Arca-style clamp) if desired. Drilled holes necessary to attach any of the flash brackets from Wimberley, Really Right Stuff & Kirk Enterprises are also incorporated into the design. This adapter is compatible with the Nikon 400mm f/2.8 AF-S Versions I and II & VR, and the Nikon 600mm f/4.0 AF-S Version II & VR.