The Kupo KS-347 is an accessory for the Kupo KCP-110 Rock's Arm.  A 5/8" (16mm) hex stud that you can mount to the end of your KCP-110 Rock's Arm, allowing you to mount into a Kupo Convi Clamp (KCP710P, KCP710B and KCP700B) or a Super Viser clamp. 

The hex shape of this connector stops the rocks arm from rotating in the clamp mount while supporting up to an 8kg light fixture or camera.