The Rain Bird® M72050 is a ESPSITEU Satellite Controller Upgrade Kit for ESP-MC and ESP-Sat Link Radio to convert to ESP-SITE SAT Controller models. The ESP-Site Satellite controller is the most versatile satellite controller yet. This controller combines the capabilities of the Cluster Control Unit (CCU) with all the power of an ESP-SAT controller. Powerful enough for large sites, yet flexible for smaller applications.