The RM21N650HD from Rectron Semiconductor is a MOSFET with Continous Drain Current 21 A, Drain Source Resistance 150 to 180 milliohm, Drain Source Breakdown Voltage 650 V, Gate Source Voltage -30 to 30 V, Gate Source Threshold Voltage 3 to 4 V. Tags: Surface Mount. More details for RM21N650HD can be seen below.