It is common for users to install and run mobile apps from microSD cards to free up device memory. Random read/write performance is therefore crucial.The application performance class was introduced to accommodate this new trend. Transcend's MicroLevel C/SDHC 300S memory cards comply with the new A1 standards.Transcend's micro/SDHC 300S memory cards comply with UHS Speed ??Class 3 (U3) and UHS Video Speed ??Class 30 (V30) standards for 4K Ultra HD video recording.In addition to excellent random read/write performance, Transcend's Micro?C/SDHC 300S memory cards come in up to 128GB of storage capacity, allowing you to keep more digital files and applications close at hand.To provide the best performance and stability, Transcend's microSD memory cards are tested to withstand extreme conditions.