microSD card: capacity and speed ratings
A suitable microSD card must meet three separate conditions: a supported format, an acceptable capacity, and the write speed class required by the device. The large number in GB answers the question of capacity. U1, U3, V10 and V30 indicate a minimum write speed. The maximum speed, printed separately, is a different measure.
For a camera, portable console or another device, its manual is the most useful starting point. Note the requirements as stated, then compare the markings on the card. This is more accurate than choosing based only on brand or the highest advertised speed in the memory cards category.
microSDHC and microSDXC: format is part of the selection
In its explanation of the markings, Lexar specifies microSDHC for capacities from 4 to 32 GB and microSDXC from 64 GB to 2 TB. That is why the letters after microSD matter along with the number. A 32 GB card and a 128 GB card can have the same physical size but belong to different formats.
Capacities of 32 GB and 128 GB show the difference in practice: the first falls within the specified range for microSDHC, and the second - for microSDXC. This is a format guide, separate from the write speed class. Whether a specific device supports the format depends on its requirements, along with the supported capacity.
When the manual sets an upper limit for capacity, it is part of the selection along with the format. If the device is specified for cards up to 32 GB, the 128 GB option is not yet a confirmed alternative for it. If it supports microSDXC and the corresponding capacity, you can compare the candidates by the next criterion - write speed.
What U1, U3, V10 and V30 indicate
According to Lexar, these classes indicate a minimum write speed. The table helps you read the numbers without confusing them with the maximum read speed:
| Rating | Minimum write speed |
|---|---|
| U1 | 10 MB/s |
| U3 | 30 MB/s |
| V10 | 10 MB/s |
| V30 | 30 MB/s |
A “up to” rating for read or write speed describes a maximum claimed value, not the same criterion as the class. So an impressive read speed cannot replace an explicit V30 requirement in the camera documentation. When comparing, list these specifications in separate rows.
Conversely, V30 alone is not a sufficient guarantee for every 4K recording mode. The mode must be supported by the specific device and card according to its requirements. Do not infer recording hours or suitability for continuous operation from these four ratings alone.
Example of a purchase requiring V30
The Lexar Professional SILVER PLUS microSDXC 128 GB is listed in the catalog as class V30. If the device manual requires V30 and supports microSDXC at this capacity, the card is a candidate to compare against its other requirements. Here, the recording rating and format are matched separately.
For a card with a different capacity, look up the specifications for that specific variant. The class of a 128 GB card does not establish the class of a 32 GB card, even if they are the same brand. In Lexar memory cards, filter by the required format, capacity, and class, then compare the remaining specifications of the specific candidates.
A short query that leads to a clear choice
A useful query includes the device model, supported format, maximum capacity, and recording requirement. For example: “I need a microSDXC card with a capacity supported by this model and V30, as specified in the manual.” Enter the specific values for your device. This way, the choice is based on comparable criteria, not one big number on the packaging.
