What’s the biggest issues with Macs? I’d say the expensive cost for a mere upgrade in storage. That’s because Apple has a proprietary SSD connector which is non-compliant with the standard M.2 which have became ubiquitous over the past years. We reviewed the Transcend JetDrive 820 here, and since Transcend announced a new JetDrive 855, we ought to take a look at it as well.

Before making a purchase, we highly recommend you to visit Transcend’s website to check for compatibility. Click here for the list of compatible Mac computers.

The JetDrive 855 is actually 2-in-1 as it comes with an external enclosure and a Transcend JetDrive 850 SSD that can be removed. You can buy the JetDrive 850 SSD alone, but you won’t get the enclosure. Learn more about it here. We highly recommend you to buy the JetDrive 855 since the external enclosure means you can repurpose the SSD to become a Time Machine backup drive or as a speedy external storage drive.

There are a few differences between the JetDrive series of Mac SSDs as well. Depending on what you need, you can opt for different JetDrives within the family. From Transcend’s website, this is what we know:

JetDrive 855JetDrive 850JetDrive 825JetDrive 820
Interface standardNVMeAHCI
PCIe versionGen. 3 x4Gen. 3 x2
Maximum performanceRead 1,600MB/s
Write 1,400MB/s
Read 950MB/s
Write 950MB/s
System requirementsmacOS 10.13 or latermacOS 10.10 or later
NoteWith enclosureSSD onlyWith enclosureSSD only

We are going to use a MacBook Air 11-inch from mid-2013 as our test subject for today. While it isn’t the fastest MacBook around, it is compatible with the entire JetDrive 800 series.


JetDrive 855 Thunderbolt SSD Enclosure
InterfaceThunderbolt 10 Gb/s
Dimensions120 mm x 31.5 mm x 18.2 mm
Weight88 grams
JetDrive 850 SSD
InterfaceNVMe PCIe Gen.3 x4
Capacity240GB, 480GB, 960GB
Storage Media3D NAND Flash memory
Maximum PerformanceSequential read: 1,600MB/s
Sequential write: 1,400MB/s
Operating Temperature0°C (32°F) ~ 60°C (140°F)
WarrantyFive-year Limited Warranty (Warranty does not apply when JetDrive Toolbox’s wear-out indicator displays 0% within 5 years.)
NoteSpeed may vary due to host hardware, software, usage, and storage capacity.


Transcend JetDrive 850 JetDrive 855

Upon receiving the Transcend JetDrive 855, I was surprised. Not by the fact that the entire box is wrapped in plastic only, but both the ends of the box actually had the plastic glued shut. Ripping the plastic off will potentially damage the box.

But, contrary to what we’ve experienced with the JetDrive 820’s super-premium box which is covered in soft-touch material inside and out, the Transcend JetDrive 855 is made out of cardboard only.

Transcend JetDrive 850 JetDrive 855

Looking at the back of the box we can find the contents of the package and also a QR code where it tells you what device is compatible with the SSD. The Transcend JetDrive 855 is also eligible for a 5-year worldwide warranty.

Transcend JetDrive 850 JetDrive 855

Opening up the box we find the Transcend JetDrive 855 wrapped in a hard-shell plastic cradle – similar to what the JetDrive 820 has.

Transcend JetDrive 850 JetDrive 855

Underneath the cradle we find the two screwdrivers – one P5 and another T5 screwdrivers to open up the MacBook and also the enclosure. There’s also a sticker pad for you to seal up the screws and to provide friction to the enclosure. More on that later.

Transcend JetDrive 850 JetDrive 855

Overall, what you get is just the Transcend JetDrive 850 SSD, the enclosure, two screwdrivers, a quick installation guide, and a friction pad to seal the screws on the enclosure.


The enclosure itself that houses the SSD inside is actually very plain. It is made out of relatively thick piece of aluminium. It’s a little weighty for its size.

Transcend JetDrive 850 JetDrive 855

There’s a bright blue status indicator LED at the front together with a Transcend logo, and the short Thunderbolt cable comes out from the other end.

Transcend JetDrive 850 JetDrive 855

The reason why they’re using Thunderbolt is actually brilliant. Since this upgrade kit is meant for MacBooks that has a Thunderbolt port (which is oftentimes unused), Transcend utilizes it with the enclosure.

Transcend JetDrive 850 JetDrive 855

Behind the SSD we can see a total of 4 screws. They’re T5 screws by the way, so you’ll have to use the included red screwdriver to open it.

Transcend JetDrive 850 JetDrive 855
There’s the JetDrive 850!

Once the enclosure is opened, we finally get to see the JetDrive 850 SSD itself, alongside with the PCB that is built into the enclosure.

Looking at the JetDrive 850 SSD, there’s really nothing too special about it. Only one side of the PCB is utilized since we’re reviewing the 240GB version.

Transcend JetDrive 850 JetDrive 855

Fun fact: the Toshiba SSD that came with the MacBook Air 11-inch mid 2013 is only 128GB and used both sides of the PCB. Technology in NAND chips sure advanced a lot over the past 5 years.

JetDrive ToolBox software

Nothing has changed at all since the first time we looked at the JetDrive ToolBox from nearly a year ago. The interface is the same – but there’s one new option which is to optimize the system for the JetDrive 850 SSD. Not sure what’s it for, though.

Transcend JetDriveToolbox for JetDrive 850 JetDrive 855

We’re unable to test the ease of firmware upgrade since the JetDrive 850/855 that we have is already with the latest firmware.

Transcend JetDriveToolbox for JetDrive 850 JetDrive 855

Installation/upgrade guide

We used the same approach as before, where we used SuperDuper! to clone everything from the existing SSD to the new SSD. Simple and straightforward, and can be done rather quickly depending on how much data you have.

Transcend JetDrive 850 JetDrive 855

Our best advise is always remember to test booting to the newly migrated system via Thunderbolt before swapping the SSDs.

The reason why we’re insistent in getting the JetDrive 825 and 855 is because of the enclosure. Once we swapped the SSDs, we can reuse the old SSD as a speedy external storage device.

We have a new upgrade guide featuring the new Transcend JetDrive 855 too. Check it out here.

Performance benchmarks

Here’s the funny thing. You can buy the Transcend JetDrive 855 and use it as an external Thunderbolt storage device – which is quite wasteful since the true potential of the Transcend JetDrive 850 SSD that is inside will not be utilized.

Transcend JetDrive 850 JetDrive 855 over Thunderbolt
The Transcend JetDrive 850/JetDrive 855 is connected via Thunderbolt.

With that said, we benchmarked the Transcend JetDrive 850 SSD through the enclosure and also as our internal SSD. We used a MacBook Air 11-inch from mid-2013 running on the latest version of MacOS 10.14 Mojave for this test.

Transcend JetDrive 850 JetDrive 855 as internal SSD
We then migrated the JetDrive 850 SSD and connected directly to the motherboard!

Through Thunderbolt port, we can see that the performance is about the same as the Transcent JetDrive 820 that we reviewed nearly a year ago. However, once we migrated our MacOS to the JetDrive 850 (which is inside the enclosure) into the MacBook Air, we see a drastic change in the read speeds.

Remember – the JetDrive 850/855 is a PCIe Gen. 3 x4 NVMe SSD, and from our tests, we know that Thunderbolt isn’t going to fully utilize its potential. With that said, the MacBook Air we are using is bottlenecking the JetDrive 850/855. We get speeds that are sub-par in conventional PCIe Gen. 3 x4 NVMe SSD speeds.

Transcend JetDrive 850 JetDrive 855

When it comes to thermals, we repeated the speed test for a long time and there was no drop in speed despite the SSD getting warm. Even the enclosure got warm, by the way.

Wrapping up the Transcend JetDrive 855 review

It’s simple – storage drives for MacBooks are expensive. If you’re looking to get larger storage and better speeds, then this is a no-brainer deal.If the JetDrive 855 is compatible with your system, then go on ahead and buy it.

Migrating your system will take a bit of time if you are inexperienced. You’ll have to connect the enclosure that has the JetDrive 850 SSD inside it first, copy everything via SuperDuper!, test booting into the new system via Thunderbolt, then swap the SSDs, and you’re done.

Transcend JetDrive 850 JetDrive 855

For the price of RM1,194 for the 240GB version at Transcend’s official LazMall store, the Transcend JetDrive 855 is only meant for those who are serious about getting an SSD upgrade for their MacBooks.


  • Super speedy
  • Comes with an external enclosure with Thunderbolt connector


  • Enclosure does not have removable cable or swappable for standard USB-A or USB-C
  • Cable is short

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