The MKG 40RK600LB from Littelfuse is a MOSFET with Continous Drain Current 54 A, Drain Source Resistance 41 milliohm, Drain Source Breakdown Voltage 600 V, Gate Source Voltage -20 to 20 V, Gate Source Threshold Voltage 2.5 to 3.5 V. Tags: Surface Mount. More details for MKG 40RK600LB can be seen below.