Neewer Professional 1/4" Thread Mount Rail Block Rod Clamp Rig for 15mm Rod DSLR Rig Support Rail System Follow Focus Magic Arm Monitor Rig Fit all 15mm rod system. DSLR rig connector with 1/4" thread. Used to connect the shoulder support, camera cage, magic arms, LED lights, flashes, LCD monitors and follow focus and so on. There's a spacer between the knob and the clamp, this can protect the clamp and the knot from scratch. Made of solid durable aluminum.