1. Long QR plate for telephoto lenses with a support foot.
2. Two screws to insure proper alignment and maximum security.
3. Rear ridge helps prevent the lens from turning, when positioned vertically, if only one screw is used.
4. Patented SIRUI safety lock design (on the QR clamp), that prevents your camera from accidentally sliding off of the head when you slightly loosen the Quick Release Clamp (to make adjustments to the positioning of your equipment).