Zacuto Z-RE-FM3.5 rod extension has been discontinued, here are some related products you might like:
3.5" male/female rod extensions. Female on one end and male on the other. 1 rod extension only. Our rods are all lightweight; 15mm diameter with 60mm spacing and clear anodizing. They are made out of 6061 aluminum and the threads are ½” 13.
More information about Zacuto Products (Link to Zacuto Website)