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While microSD cards are still dominating the market, the amount of choice can be quite jarring. Today, we have a special little microSD card in the labs – and that is the from the Transcend 300S series of microSD cards.

The full name of this microSD card is jokingly long. There are terms like microSDXC, UHS-I U3, V30, A1 – but what do they all mean? Well, you can click here and here to learn about some of them. But you just need to pay attention to the terms V30 and A1.

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Transcend 300S MicroSD card (TS128GUSD300S-A)

The box itself is rather simple for a microSD card. It is just a simple cardboard seal that requires you to break the packaging if you want to access the contents.

Transcend 300S MicroSD card (TS128GUSD300S-A)

At the back of the packaging, we can see a bit more information here… but not really useful since there are no specs stating its sequential read/write speeds and the random read/write IOPS. Also, if you understand the terms used to specify the specs of microSD cards, then you already sort of know the speeds of the microSD card.

Transcend 300S MicroSD card (TS128GUSD300S-A)

Opening up the packaging obviously reveals the adapter and also the Transcend 300S microSD only. Transcend does sell another variant of 300S without the adapter.


I did this performance test in two different perspective – one as a SSD-like portable storage device. Another one is with my phone. Essentially, the specification for the Transcend 300S microSD card has specified that it has a sequential read speed of up to 95MB/s and has the sequential write speed of at least 30MB/s (V30 rating).

Benchmarks using USB 3.0 card reader

Here we are using a USB 3.0 card reader with my desktop PC. We ran the standard test by using CrystalDiskMark first.

Here we can see that the sequential read/write speeds are pretty much in line with what the Transcend 300S microSD card has promised us. It has the sequential read speeds just shy of 95MB/s. According to the V30 specification, it needs to be at least 30MB/s of sequential write speed – and the Transcend 300S microSD crushes that speed. However, since it did not reach the 60MB/s mark, it can only be rated as V30.

As for random IOPS, the Transcend 300S microSD is exceptionally good and it hits around the 10MB/s mark for all random 4K tests. The high random 4K access speed is actually what the “A1” means on the Transcend 300S microSD’s packaging.

The A1 standard is created to certify that a microSD is fast enough for Android phones to use as it is meant for apps to be moved to the external storage, hence freeing some space for your internal storage. However, apps are broken into small chunks – hence the speedyt random 4K access speed is necessary.

Benchmark using a smartphone

The smartphone of my choice is the Samsung Galaxy S9. I’ve been using it for nearly a year now and my internal storage is pretty much filled to the brim. However, microSD card benchmarks on Android is pretty much CrystalDiskMark on a phone. My benchmark tool of choice is AndroBench, and it reveals this result:

Transcend 300S microSD CrystalDiskMark benchmark

It does appear to be slower on the phone too – and that might be because of how much crap I have running in the background already. Whichever the case may be, the microSD card still performs well. It is scoring around 75MB/s sequential read and around 45MB/s sequential write speed, and scoring in at 7MB/s for random 4K read and around 5MB/s for random 4K write speeds.

Wrapping up the Transcend 300S microSD card review

These results only tell us one thing – for power users of Android smartphones, the Transcend 300S microSD is obviously highly recommended in our books. It has fantastic sequential read and write speeds, making it really suitable for 4K @ 60FPS video recording with a smartphone. I personally use Filmic Pro on the Galaxy S9 to film all videos from events. Click here to watch those videos.

Transcend 300S MicroSD card (TS128GUSD300S-A)

Then onward to the random 4K access times. It does affect our day to day user experience as it can take much longer to show all the picture thumbnails in the gallery – especially when there are thousands of pictures in your microSD card. The high random 4K read and write speeds means that you can move apps, pictures, and games to your microSD card without suffering from a long loading time.

Transcend 300S MicroSD card (TS128GUSD300S-A)

Of course, with 128GB, you can even use your Android smartphone like a USB drive. Just transfer your data into your phone and bring it with you.

Transcend is currently offering the 300S microSD in both 128GB and 256GB variants too. However, I can only find the 128GB in the market – and it is priced at only RM99. That is much cheaper than Huawei’s NM cards.

Where to buy?

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