AC-CSLSK2 clamp with cut outs on top and bottom.
The cut-out will give it so much further flexibility and is great for making better configuration options for your arms.
It meassures 3-inces/10cm from center to center. The length allows it to reach out over the flatport, and will therefore also be good for a focus light.
Can also be used with thick boyancy arms to keep them apart and at the sam time give good flexibility.