Sonnet's Fusion Flex J3i Mount Lets You Add Up to Three Internal Drives to Your Mac Pro

Sonnet today announced the upcoming launch of its Fusion Flex J3i internal drive mount for the 2019 Mac Pro, which lets users add up to three SATA storage drives to their machines.

sonnet fusion flex installed
Sonnet isn't the only company to launch an internal drive mount for the new ‌Mac Pro‌, and Apple itself sells Promise's Pegasus J2i system that lets you add two drives, but Sonnet says it's the first to let users add three drives right inside the ‌Mac Pro‌ and connected directly via SATA.


The Fusion Flex J3i offers two slots that can accept either 3.5-inch hard disk drives or 2.5-inch SSDs, and a third slot that accepts a 2.5-inch SSD, allowing for a total of 36TB of additional internal storage.

Storage installed via the Fusion Flex J3i won't be as fast as the main NVMe SSDs at the heart of the ‌Mac Pro‌ or PCIe-based storage upgrades, especially if you're using traditional hard disk drives, but if you're a user who wants to prioritize storage space and simplicity over drive speed, Sonnet's Fusion Flex J3i might be worth checking out.

sonnet fusion flex kit
The Fusion Flex J3i includes the mount, required power/data cable assemblies, and mounting brackets to fit 2.5-inch drives into the 3.5-inch drive slots, but the drives themselves are sold separately. It will be priced at $199.99 and launches on June 15.

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Top Rated Comments

Rychiar Avatar
31 months ago
wait these things don't allow more than one in the first place??
Score: 8 Votes (Like | Disagree)
WildCowboy Avatar
31 months ago

wait these things don't allow more than one in the first place??
The stock storage is either one or two Apple-proprietary storage modules tied to the machine's T2 chip. You can go up to 8TB total with those.

Beyond that, it's either PCIe-based storage, internal SATA like this, or external options.
Score: 8 Votes (Like | Disagree)
Darth Tulhu Avatar
31 months ago
There was a time when I would drool over stuff like this (I still kinda do).

My days of popping the hood are behind me (even though I've been keeping my 2011 17", and 2012 iMac and 15" alive for the last couple of years with those skills).

I'm amazed that we live in an age where I can ACTUALLY replace my hardware with an iPad!

I no longer need the power this machine offers, even if I think it's cool that it can provide it.
Score: 8 Votes (Like | Disagree)
Stang Avatar
31 months ago
$200 for a piece of plastic and 3 sata cables? Yikes.
Score: 8 Votes (Like | Disagree)
SSDGUY Avatar
31 months ago

wait these things don't allow more than one in the first place??
I believe they can take two drives without an expansion mod.
Score: 5 Votes (Like | Disagree)
theluggage Avatar
31 months ago
$200 for a mounting bracket and 2 slightly-customised SATA cables that should have been included with the Mac in the first place...

To be fair, the third cable is a USB3-to-SATA cable which might set you back as much as $7!

Sheesh. I've bought entire PC cases that cost less than $200 and they don't charge extra for the flippin' drive brackets. ...and that's premium Fractal Design/Silverstone stuff that you can compare with Apple and keep a straight face, although the Mac Pro blows right past "premium" and into "over-engineered to the point of parody"...

OK, I know all the big IT firms will charge you $50 for a cable tie if they think you're ordering with a corporate credit card and not watching the price, but that doesn't make it right - and they're usually doing it to compensate for under-bidding on support contracts.


Super weird how the third caddy connects via and internal USB3 cable, rather than SATA like the other two.
...probably because there are only 2 SATA connectors (plus a USB-3) on the Mac Pro mainboard...?
Score: 5 Votes (Like | Disagree)

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