The STL120N4F6AG from STMicroelectronics is a MOSFET with Continous Drain Current 55 A, Drain Source Resistance 2.9 to 3.6 Milliohm, Drain Source Breakdown Voltage 40 V, Gate Source Voltage -20 to 20 V, Gate Source Threshold Voltage 2 to 4 V. Tags: Surface Mount. More details for STL120N4F6AG can be seen below.