The CAP CER 3.9PF 100V C0G/NP0 0402 is a small ceramic capacitor with a capacitance of 3.9 picofarads and a voltage rating of 100 volts. It belongs to the C0G (NP0) class, which offers low losses and a temperature-stable capacitance value. This component comes in a metric size of 0402 (1005), making it suitable for compact designs and surface mount applications.