I was randomly searching ebay for a scuba tank and I came across this "Tank Saver". I understand that the O Ring can fail but I don't see how this "Tank Saver" can fix the tank to save it from being tossed. Plus I can't imagine a tank being thrown away just because it leaks at the O Ring. Replace the O Ring and you are back in action. At least that is what I thought. This seller has sold a few of these with positive reviews. This one is up with an initial bid of $20. I do not have AL tanks and the auction only discusses AL tanks so I guess I would not need it but I am curious is this would be useful at all and how would it be useful. Also, I am wondering if anyone here has this sort of device. I am not the seller trying to find another way to sell this device nor am I in any way affiliated with the seller. I am just curious if someone is a swindler and found a way to sell pet rocks to scuba tank owners or if this is a useful tool to have.