The STP20NK50Z from STMicroelectronics is a MOSFET with Continous Drain Current 17 A, Drain Source Resistance 230 to 270 Milliohm, Drain Source Breakdown Voltage 500 V, Gate Source Voltage -30 to 30 V, Gate Source Threshold Voltage 3 to 4.5 V. Tags: Through Hole. More details for STP20NK50Z can be seen below.