Many users encounter annoying issues when shooting 4K video: recording stops unexpectedly, video files get corrupted, or games lag heavily when stored on microSD cards. In most cases, the root cause is that your memory card fails to meet official speed class standards set by the SD Association.

Markings including U3, V30 and A2 represent three independent performance standards. Many buyers confuse these labels and end up losing valuable footage. This guide explains the definition, differences and applicable scenarios of each rating to help you pick the correct memory card for cameras, drones, action cameras and game consoles.

Minimum sequential write speed: 30MB/s.

U3 is a general high-speed standard for UHS-I / UHS-II cards, suitable for burst shooting and short-duration HD video recording. It sets a baseline continuous write requirement but lacks long-duration video stability testing.

Minimum sustained sequential write speed: 30MB/s.

V30 is specially designed for continuous video capture. Cards under V30 certification pass strict long-time recording load tests. It is the minimum requirement for stable 4K video recording on action cameras and drones.

Random read ≥4000 IOPS, random write ≥2000 IOPS.

A2 focuses on random read/write performance for small files. This rating improves app launching speed and game loading performance for consoles and Android devices. It does NOT boost continuous video writing speed.

Always check your device official manual for official memory card requirements. For 4K videography, choose microSD cards marked U3 + V30. Select A2 if you run applications directly from your memory card.