View czrw5221b-g thru czrw5259b-g datasheet:

Surface Mount Zener Diodes CZRW5221B-G thru CZRW5259B-G Voltage: 2.4 ~ 39 Volts Power: 500 mW Features: Planar Die Constructions SOD-123 500mW Power Dissipation .154 (3.90) .141 (3.60) Zener Voltages from 2.4V ~ 39V .110 (2.80) .098 (2.50) Ideally Suited for Automated Assembly Processes Mechanical Data: Case: SOD-123, Molded Plastic Terminals: Solderable per MIL-STD-202, Method 208 Polarity: See Diagram Below Mounting position: Any Approx. Weight: 0.008 gram .016 (.40) Min. .005 (.12) Max. Dimensions in inches and (millimeters) Maximum Ratings and Electrical Characterics Parameter Symbols Value Units Power Dissipation (Note A) at 75oC PD 500 mW Peak Forward Surge Current Surge, 8.3ms Single IFSM Half Sine-Wave Superimposed on Rated Load 4 A (JEDEC Method)