The SSM3K121TU from Toshiba is a MOSFET with Continous Drain Current 3.2 A, Drain Source Resistance 36 to 140 Milliohm, Drain Source Breakdown Voltage 20 V, Gate Source Voltage -10 to 10 V, Gate Source Threshold Voltage 0.35 to 1 V. Tags: Surface Mount. More details for SSM3K121TU can be seen below.