OWC Express 4M2 Ultra: The First Certified Thunderbolt 5 Four-Slot NVMe Enclosure

OWC has launched the Express 4M2 Ultra, which the company describes as the first certified Thunderbolt 5 four-slot NVMe M.2 SSD enclosure. Announced at NAB 2026, it is aimed squarely at people who move large files for a living and have run out of patience with Thunderbolt 4.

It is a genuinely interesting product, but it is also a specialist one. Here is what it does, who it suits, and what an Australian buyer should think about before ordering.

What the Express 4M2 Ultra is

It is an empty enclosure. You supply four NVMe M.2 SSDs, install them, and the enclosure presents them to your Mac over Thunderbolt 5 either as separate volumes or as a single RAID array.

The published specifications are:

• Interface: dual Thunderbolt 5 ports
• Speed: up to 6,622 MB/s in real-world use, according to OWC
• Capacity: four M.2 slots taking 2280 or 2242 NVMe SSDs, up to 32TB total
• RAID modes: RAID 0, 1, 4, 5 and 10, or JBOD, configured through SoftRAID
• Compatibility: backward compatible with Thunderbolt 4, Thunderbolt 3 (Mac) and USB4
• Daisy chaining: up to five devices
• Build: aluminium chassis with an adaptive fan

OWC has quoted US pricing of USD $399.99 for the enclosure, and USD $549.99 for a bundle including SoftRAID. Those are United States prices. Australian pricing had not been announced at the time of writing, and we would not encourage anyone to convert the US figure and treat the result as what it will cost here — freight, GST and distribution all sit between the two.

Why four slots and Thunderbolt 5 matter together

A single fast NVMe SSD can already saturate Thunderbolt 3 and comes close on Thunderbolt 4. That is the reason a lot of single-drive Thunderbolt enclosures feel similar to each other in practice — the bottleneck is the port, not the drive.

Thunderbolt 5 raises the ceiling substantially, and a four-drive striped array is one of the few storage configurations that can actually reach up towards it. That is the logic behind this product: four drives working together, on a bus fast enough to let them.

The corollary is that if you only need one drive's worth of speed, you do not need this. A good single-slot Thunderbolt enclosure will be cheaper, smaller and silent. Our Thunderbolt and USB-C SSD drives page covers those options.

Choosing a RAID mode

The RAID flexibility is the real appeal, and it is where most buyers make their decision badly. The short version:

• RAID 0 stripes across all four drives for maximum speed and maximum capacity, with no redundancy at all. One drive fails and the entire array is gone.
• RAID 5 keeps parity across the drives, so the array survives a single drive failure while still giving you most of the capacity. This is the sensible default for working storage.
• RAID 1 and RAID 10 mirror data, trading capacity for redundancy.
• JBOD presents the drives individually, which suits people who want four separate project volumes.

It is worth stating plainly, because it catches people out every year: RAID is not a backup. Redundancy protects you from a drive failing. It does nothing about accidental deletion, a corrupted project file, ransomware, theft or a power event that takes the whole enclosure. A redundant array still needs a separate backup somewhere else.

If you are weighing up array types more broadly, our RAID storage range for Mac covers two-bay through eight-bay options, and our guide to understanding RAID goes through the levels in more detail.

Don't overlook the cable

This is the most common way people lose performance on Thunderbolt storage, and it costs nothing to avoid.

Thunderbolt 5 speeds require a cable rated for them. A USB-C cable that charges your laptop perfectly well may carry data at a small fraction of the rate, and nothing on screen will tell you that is happening — you will simply think the enclosure is slower than advertised. If you are buying hardware at this level, buy a certified cable to go with it. Our Thunderbolt cables range covers the certified options.

Which Macs benefit

Thunderbolt 5 is a recent addition to the Mac line, so the full speed of this enclosure is only available on Macs that have Thunderbolt 5 ports. Check your specific model's specifications rather than assuming, as the ports look identical to Thunderbolt 4 and USB-C.

On an older Mac, the enclosure still works — it falls back to Thunderbolt 4, Thunderbolt 3 or USB4 speeds. Whether that is a sensible purchase depends on your plans. If you are replacing the Mac within a year or two, buying storage that will not be the bottleneck later is defensible. If you are not, you are paying for headroom you will not use.

Security tip: fast storage still needs protecting

An enclosure like this often ends up holding the only copy of a client project. Speed is not protection, so a few habits are worth building in from day one:

• Encrypt the volume. Format it as APFS (Encrypted) in Disk Utility, or turn on encryption when you create the array. A portable enclosure full of client footage is a data breach waiting to happen if it is lost or stolen.
• Keep a copy somewhere else. RAID survives a drive failing; it does not survive ransomware, a deleted folder, theft or a power surge. The old rule still holds — three copies, two media types, one off-site.
• Eject properly. Pulling a Thunderbolt enclosure mid-write is one of the more common ways people corrupt an array, and a parity rebuild is not a backup either.
• Wipe it before it leaves your hands. If you sell or repurpose the enclosure or its drives, erase them properly rather than dragging files to the Bin.

Is it available from Macfixit?

Not at the time of writing. OWC indicated Q3 2026 availability, and we have not listed the Express 4M2 Ultra yet.

We do stock a broad range of OWC storage, Thunderbolt docks and enclosures, and we can advise on what is currently available here. If you are planning a storage upgrade and want to know what makes sense for your particular Mac and workflow, get in touch with our team rather than guessing from overseas announcements.

The short version

The Express 4M2 Ultra is a four-slot, Thunderbolt 5, RAID-capable NVMe enclosure aimed at video and photography workflows where sustained throughput genuinely matters. Pricing announced so far is United States pricing, and Australian availability has not been confirmed. If you need a single fast external SSD rather than an array, there are simpler and cheaper ways to get there.

Sources

• OWC – Other World Computing Launches OWC Express 4M2 Ultra at NAB 2026 – press release
• VP Land – OWC Debuts First Certified Thunderbolt 5 Four-Slot NVMe Enclosure at NAB 2026 – vp-land.com
• OWC – Other World Computing Announces Fully Certified 2-Meter Thunderbolt 5 (USB-C) Cable – owc.com
• MacRumors – CES 2026: OWC Launches 2-Meter Thunderbolt 5 Cable for Macs – macrumors.com