The Photo Clam PC-102-UP Mounting Plate is designed for long telephoto lenses, such as 400mm, 500mm & 600mm models. Attaching to the foot of the lens collar, the 6.7"-long plate has two adjustable screw positions so you can find the proper balance for your specific lens.
The Arca-style dovetail plate is machined in Korea from 6061 T6 aircraft-grade aluminum and features a stainless steel screw.