The BZX584B4V3 from Micro Commercial Components is a Zener Diode with Zener Voltage 4.21 to 4.39 V, Zener Current 5 mA, Voltage Forward 0.9 V, Current 1 mA, Current Reverse Reverse Leakage Current:- 3 uA. More details for BZX584B4V3 can be seen below.