This is a 500V ceramic capacitor with the designation CAP CER 1PF 500V C0G/NP0 0603. It has a capacitance of 1 pF and an accuracy of ±0.1pF, making it suitable for applications requiring precise capacitance values. The C0G material is known for its stability over temperature and voltage changes, while the NP0 designation indicates that it meets specific performance criteria.