SD cards have various codes and symbols to indicate their speed class, application performance class, and UHS bus interface. For example: - A number inside a circle (e.g., 10) indicates the Speed Class. - A number inside a U (e.g., U1 or U3) indicates the UHS Speed Class. - A number following a V (e.g., V30, V60, V90) indicates a newer (and faster) UHS Speed Class rating. - A number following an A (e.g., A1 or A2) indicates the Application Performance Class. Roman numerals (I or II) represent the UHS Bus Interface, with I being UHS-I and II being UHS-II. - To determine the performance and compatibility of an SD card, consider these symbols and consult your device's specifications.