MicroSD memory cards expand the file storage of mobile devices such as cameras and phones and other devices with a MicroSD slot.
These particular MicroSD cards are rated as up to UHS-I Class 3 (U3), meaning they can write at up to 30MB/sec making them suitable for recording 4K or FullHD (1080p) video at 60 - 120fps and high resolution photos. Some of these cards are also rated as V30 Video Speed, labelling them as being optimised for video recording.
Some cards even feature an Application Performance Class, making them ideal for use with devices such as tablets & smartphones. Cards labelled A1 provide a minimum of 1.5k Read & 0.5k Write IOPS, while A2 labelled cards push random performance even further with a minimum of 4k Read & 2k Write IOPS.