The ZVX 4 S 0603 300 from Bourns is a Varistor with AC Voltage Rating 4 V, DC Voltage Rating 5.6 V, Clamping Voltage 15.5 V, Capacitance 165 pF, Temperature Operating Range -55 to 125 Degree C. Tags: Surface Mount. More details for ZVX 4 S 0603 300 can be seen below.