For Canon: 100-300 RF f/2.8 IS
                    400 f/2.8 IS III
                    400 RF f/2.8 IS
                    800 RF f/5.6 IS 

The AP-601 Replacement Foot fits 400 f/2.8 IS III Canon lenses and serves three main purposes:

1. Added Stiffness over the factory tripod mounting foot connected to a lens plate, reducing flex and vibration.
2. Functions as the Arca-Swiss style quick-release plate for your lens.
3. Creates a more ideal geometry for using your lens on the Wimberley Sidemount Head and Sidekick, allowing the lens to balance optimally.

Wimberley lens plates are compatible with Arca-Swiss style quick-release clamps such as those made by Wimberley, Kirk Enterprises, Really Right Stuff, Arca-Swiss, Markins and others.