Battery Distribution Cluster f/Twin Engine w/Two Battery BanksThe 715-S allows you to switch the house loads between port and starboard batteries. You can also use the selector switch to parallel the batteries .WARNING: This product can expose you to chemicals including di(2-ethylhexyl)phthalate (dehp) which is known to the State of California to cause cancer, birth defects or other reproductive harm. For more information go to P65Warnings.ca.gov.