Solenoid valves direct the flow of fluid to the actuators. The solenoid valves lock tightly to secure the tabs in place. WARNING: This product can expose you to chemicals which are known to the State of California to cause cancer, birth defects or other reproductive harm. For more information go to P65Warnings.ca.gov.This product may not be returned to the original point of purchase. Please contact the manufacturer directly with any issues or concerns.