The ML4661 from Spectrum Control is a RF PIN Diode with Insertion Loss 0.5 to 0.7 dB, Isolation 20 to 25 dB, Reverse Current 10 uA, Breakdown Voltage 40 to 60 V, Thermal Resistance 60 to 80 Degree C/W. Tags: Chip. More details for ML4661 can be seen below.