It’s a corner block for GAMMA’s 290mm truss. It does what it’s supposed to 🙂
From the Manufacturer:
Our GT-290mm 6 Way Cube is a perfect corner/junction piece. Having the capability to connect 6 pieces of our 290mm truss. When purchased, it comes with 8 connectors which is enough for 2 sides of the 6 way cube. Additional connectors can be purchased in our “Accessories” section.
