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, if only one screw is used. 4. Stop screws on the bottom of the QR plate prevent 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). 5. Arca-compatible. 6. Standard plate supplied with SIRUI PH-20 Gimbal Head.