The PH-120 Quick Release Plate from Sirui is an Arca-compatible plate designed for use with telephoto lenses with a support foot. It has a ridge at the rear of the plate that helps keep the lens from turning if only one mounting screw is used. Four anti-slide mats on the surface keep the lens in place while installing the plate. It uses a dual mounting screw design to properly secure your rig. On the bottom of the plate are two screws, one at each end, that prevent the plate from accidentally sliding off the head if the quick release clamp is loosened