The part number CAP CER 1UF 4V X5R 0402 refers to a specific type of ceramic capacitor. This component is characterized by its capacitance value, which is 1 microfarad (µF), and it operates within a voltage range of ±20 4V. It has an X5R rating, indicating that it falls under the category of X5R ceramics. The metric size designation for this capacitor is 0402, also known as 1005 in some notations.