Nothing too special about this except it's universal compatibility with 4 different vises in my shop.
The ends of the main 3/8 diameter rod have two different threads. 5/16-24 on one end of each allows them to be used on the Wiltons which I drilled and tapped for 5/16-24. One end has 1/4-20 for use with one of my machinist vises. The other and last end has a 6mm x1mm for the newer machinist vise. Now I have two main rods for all my vises. I made one clamp from 1018 and all of the rods are just drill rod. One of the secondary rods has a brass end that is useful for very small parts that might be missed by the secondary rod holders. It is just threaded on to the rod. I will probably make another clamp if the need arises.