The BZT55C4V3 from Micro Commercial Components is a Zener Diode with Zener Voltage 4.0 to 4.6 V, Zener Current 1 mA, Voltage Forward 1.5 V, Current 5 mA, Current Reverse Reverse Leakage Current:- <1.0 - <20 uA. More details for BZT55C4V3 can be seen below.