Fotasy MAC 11-Inch Articulating Magic Arm for Mounting HDMI Monitor LED Lights with 15mm Rod Clamp (Black) This is an professional 11''articulating arm with 15mm rod clamp It is perfect for mounting your hd monitor, led video lights to DSLR RIG ROD Rail system, rail support. Durable construction with a locking control knob to release or engage the tension, this articulating arm simplifies the mounting, placement and adjusting any on-camera lighting and other accessories. Ergonomic design, one knob locks all positions.