This pair of Shape 15 mm Aluminium Rods (12") connect into your camera rig, extend it, and let you add various Shape and third-party accessories compatible with 15 mm rods. With these two rods and with a few fundamental accessories, you can most certainly even begin building your own rig from scratch.
The rods are each 15 mm in diameter, 12 inches(30.5 cm) long, hollow, non-threaded, and made of reliable aluminium coated with a clear finish.