Provides uninterrupted pumping in the event of a power outage or main pump failure;Fully assembled;Primary pumps available in 1/3 and 1/2 hp;Ready to connect to 1-1/2" discharge pipe;System includes primary pump check valve and back-up pump check valve;Suitable with AGM, Wet Cell or Gel type batteries (not included);Liberty Pumps StormCell batteries recommended for optimum performance