The CSM166-4 from ISOCOM is a RF Transistor with Supply Voltage 0.7 to 1.8 V(Forward Voltage), Collector Current (Ic) 100 mA, Power Dissipation (Pdiss) 150 mW, On Resistance 10 Ohms, Operating Temperature -55 to 125 Degree C. Tags: Flatpack. More details for CSM166-4 can be seen below.