C2 is the slowest speed class while C10 is the industry standard. Because of newer hardware devices requiring newer speed classes with higher speeds and capabilities, hardly anyone uses Class 2–6 nowadays. C10 is usually the minimum speed class requirement for most hardware devices made today.

MicroSDHC cards are microSD cards with at most 32GB, while microSDXC card have more than 32GB storage capacity. You can mainly use a microSDHC card to store media in Full HD quality and a microSDXC card for 4K images or large bulks. There's not much difference in terms of read and write speeds.

The Class rating is the minimum write speed. A Class 4 memory card supports sustained writing at 4MB/s or better; a Class 10 memory card supports sustained writing at 10MB/s or better. The original Class system only goes to 10MB/s.

While you can use any class of microSD cards in your phone or tablet, the microSDXC card is recommended for high-resolution video recording, due to its large storage capacity and high-speed read and write capability.