Maybe your original base unit was damaged, or you’re upgrading an older setup to the A3 platform. Either way, this A3 Apex Pro Base Unit is exactly what you need. Plug all of your current Neptune Systems accessories into it like the EB832 Energy Bar, Apex modules, or pH and temperature probes. If your tank already runs on Apex, this is the easiest way to upgrade or get everything back up and running without having to buy the full controller kit.