Unlike most solenoid valves, this is a latching solenoid valve. Latching solenoid valves have one distinct advantage: they draw no power when the valve is open (or closed), only during the transition between each state. This is particularly advantageous when battery power is involved. Send a 30ms (min) pulse of 5V power down the line and it will latch open. Send a 30ms reversed polarity pulse down the line and it will latch closed. No constant power is required to hold the valve open or closed.