The MCQ4503B from Micro Commercial Components is a MOSFET with Continous Drain Current -4.4 to 5.6 A, Drain Source Resistance 19 to 66 milliohm, Drain Source Breakdown Voltage -30 to 30 V, Gate Source Voltage -12 to 12 V, Gate Source Threshold Voltage -1.4 to 1.5 V. Tags: Surface Mount. More details for MCQ4503B can be seen below.