then there was the previous version that had just an o ring. I'm not sure what got mine- where the wires go through the manifile was heavily corroded. When I tried to pull the anode down, it would not budge and ended up cutting the wires to get it off- I had the original design which had no drainage holes in it which I think was a problem on the out side. Also, the leak I had, hopefully past tense when it all goes back together, water was sitting in the bottom there and probably corroded where the wires go through from the inside. Manifold was corroded on both sides.I was able to clean that up and I will put some sealant on that gasket to make sure nothing is leaking through there....new version also has drain holes in it, the old would just puddle it. Another thing I'm learning about this system is that it draws voltage when the boat is off and out of the water and the newer version of this anode apparently draws more voltage. My batteries are often dead if I leave the boat sit a couple of weeks. I'm sure there is other stuff drawing voltage as well.