The ML400 Topside can be used as a main panel with the EL2000 AND EL1000 systems. The Balboa ML400 4 button topside also works in conjunction with the Balboa HPEL1K Spa Pack. It was used on Hydropool Self Clean and Serenity Gold Series spas as well as the AquaPlay Swim Spas from 2004 and up to and including 2011.
