The BAS521 from Nexperia is a Power Diode with Forward Current 0.25 A, Forward Voltage 0.95 to 1.1 V, Reverse Current 0.00015 mA, Repetitive Peak Reverse Voltage 300 V, Non-Repetitive Peak Forward Current 4.5 A. Tags: Surface Mount. More details for BAS521 can be seen below.