UHS (Ultra High Speed) Class is a standard that refers to higher speed classes of memory cards. UHS-I, UHS-II and UHS-III are different variants that provide different minimum write speeds, ranging from 104 MB/s to 624 MB/s. These cards are ideal for professional video and photography applications where fast and reliable performance is required. UHS classes are also accompanied by U1 and U3 classes, which indicate specific minimum speeds of 10 MB/s and 30 MB/s respectively.