My old RainBird 4 station controller of 30 years was acting crazy so I changed it out to this model. It was an easy install, has many different watering options for each zone and is a user friendly design.  I noticed the backup battery was hidden so I called Rainbird support. My old timer had a 9 volt battery that could be changed. The battery in this SST 1200o cannot be changed, so when it goes bad the unit will have to be reprogrammed after every power outage...not good. Support said it's a rechargeable lithium battery. The outdated  manual that comes with it is for an 8 zone model, and is the same on their website. The connectors for the station wire are push in connection type, so rigid wire is needed. The unit measures 9 x 9.5 x 4.5 inches.