The ML4653 from Spectrum Control is a RF PIN Diode with Forward Current 10 to 40 mA, Reverse Current 10 uA, Breakdown Voltage 600 to 650 V, Thermal Resistance 10 to 20 Degree C/W, Forward Resistance 0.8 to 1 Ohms. Tags: Surface Mount. More details for ML4653 can be seen below.