EMZETT.microSD Cards
In short: A smaller form factor of the SD card, common in smartphones, tablets, single-board computers (e.g. Raspberry Pi) and action cameras.
In more detail: microSD cards are electrically compatible with normal SD cards and can also be plugged into normal SD card slots via a simple mechanical adapter. They follow the same capacity and speed classes as regular SD cards.
In Depth
Same technology, smaller form factor
microSD cards follow exactly the same electrical and logical specification as their larger SD card relatives — the only fundamental difference is the physical size, at about 15×11 mm only a quarter the size of a normal SD card (32×24 mm). This miniaturisation made it the standard storage medium for devices where every millimetre of space counts: smartphones (if a card slot is still present at all — many newer models forgo it in favour of more internal, permanently soldered storage), action cameras, drones and single-board computers like the Raspberry Pi, where the microSD card often even serves as the primary operating-system drive rather than just additional storage.
Speed and capacity classes
As with regular SD cards, the same speed and capacity classifications apply, stating how fast data can be written — relevant, for example, when filming at high resolution, where a card that’s too slow can’t keep up with the continuous data stream, causing recordings to stop or image errors to appear. For use as a Raspberry Pi system drive, besides pure sequential speed, random I/O performance (many small, scattered read/write accesses, as constantly generated by an operating system) is also crucial — individual card models can differ considerably here despite having the same official speed class, which in practice often leads to a noticeably different perceived “speed” of the overall system.
The mechanical adapter
The included adapter for normal SD card slots contains no electronics of its own — it merely mechanically connects the contacts of the smaller card with those of a normal SD card slot, which is why speed and capacity depend exclusively on the microSD card itself, not the adapter. A cheap, poorly made adapter, however, can cause connection problems or data errors through poor contact, which is why it’s worth paying attention to brand quality for reliable use.
Wear and reliability
Flash memory cells (the underlying technology for both SD cards and SSDs) wear out minimally with every write operation — after a certain number of write cycles, individual memory cells can fail. For most everyday applications (photos, occasional videos), this lifespan is practically no problem; with sustained operation involving constant overwriting (e.g. as a system drive with frequent log writes), it can, by contrast, become relevant — special “high endurance” cards are designed for exactly such sustained-load scenarios and correspondingly more durable, but also more expensive.
See also: SD Cards