x3 on the SeeLevel gauges. The usual gauges installed especially in the black tank will generally give false readings and show full when it is not even half full. Anything in the tank that gets stuck on them will turn them on. These sensors are just switches that turn on when water connects the bottom connection to a sensor above. Toilet paper or whatever in the tank that is caught above will turn on the switch. I get fairly accurate readings on all gauges except the black tank. At some point I will make the change to the external SeeLevel system.