This is a CAP CER 18PF 2.5KV C0G/NP0 type ceramic capacitor with a value of 18 pF and a tolerance of ±2%. It has a working voltage rating of 2500V (2.5kV) and is available in the metric size 1808, also known as 4520. The designation C0G refers to the temperature characteristic of this type of capacitor, which is known for its high stability over a wide range of temperatures.