The following topside(s) are compatible with the above circuit board: 58-355-4050, 58-355-4145, 58-355-4150 Ultimate Plus Series Repl. Circuit BoardOEM Unit for Baja Spas and Whitewater Spas This board was manufactured for current production Baja Spas andWhitewater Spas with an OEM processor. Temperature and hilimit sensors sold separately