This is a 18pF 500V C0G/NP0 ceramic capacitor, specifically the CAP CER 18PF 500V C0G/NP0 1812 type. It features a capacitance of 18 pF and can withstand voltages up to 500V. The C0G/NP0 designation indicates that it is made from a high-quality ceramic material with stable properties, ideal for applications where temperature stability is crucial.