One Rail has a screw Knob Width Adjustment 2nd Rail is a Lever Clamp w Lock. Remove your existing clamp and replace it using the 6mm hex screw provided. Will fit many brands of ball heads including Arca, RRS etc. Use included Metric 6 flat head screw to mount onto a ballhead. Model: DLC-60 Jaw Length: 60mm Width: 87mm Thickness: 15mm Screw: M6 Thread: UNC3/8" Net Weight: 127g 3/8" Standard thread will fit on any standard tripod or head 1/4" steel adapter (included) converts it to 1/4" thread. All metal construction Includes bubble level