I believe that you are talking about the aluminum tubing on the end of our arm? Anyway, it is like I said some 3/4? I forget the specific size, aluminum tubing. It is actually part of our grabbing method, the "hoop" stabilizes the tetra once we have it grabbed with our hook. It is surprisingly strong and take a hit, but we will be making spares in case it happens to get crushed or something
If thats not what you were talking about, then the only other thing I could think you might mean is the turret at the base of the arm.