I looked at that tech thing too and didnt like it. I figured out how they worked and developed several work arounds. They work similar to a ballpoint pen except vacuum is applied from the back instead of pushing it with your finger. And you dont "press" all the way for lock, just half way. So you can apply half as much vacuum for lock, etc. For a couple years I had a vacuum line running from the hubs to inside the cab with a guage attaced. I could vary the amout of vacuum to switch the hubs where I wanted. I also rigged up a pressure regulator (with the pressure source from the spare tire) and applied it to the hole on the outside of the hub. This would work when the bearing seals got leaky which allowed vacuum to excape and not operate the hubs. I also determined that one could pry off the outside screen, tear a hole in the exposed rubber diaphram and poke a thin metal object (screwdriver) and operate it, deeper or not so deep, to get them to lock or unlock. But in all, I like the ones you buy better... I understand they tend to fall of sometimes, maybe cause theyre a little heavier. I put a hose clamp around the plastic fingers to help stop that, just a thought.