Fledging Shell USB 3.1: A small, fast and portable M.2 NVMe to USB 3.1 enclosure

Faster than your garden-variety Gen 2 portable SSDs, but still limited by USB's bandwidth.

fledging shell primary

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At a Glance
  • Shell USB 3.1 NVMe to USB 3.1 10Gbps (1TB)

The Fledging Shell is a small but solidly engineered enclosure that lets you leverage M.2 NVMe SSDs for increased performance. USB 3.1 Gen 2 (10Gbps) is capable of more speed than SSDs such as Samsung’s T5, Sandisk’s Extreme SSD and others deliver. Internally, those drives still utilize the older SATA protocol, which maxes out at around 450MBps in real world transfers—well below Gen 2’s theoretical limit.

The Shell provides a nice boost over the competition, but alas, also exposes USB 3.1’s limits. It’s hardly slow, but Thunderbolt it ain’t.

Specs and design

The Shell is available in the four different capacities: 256GB ($135 on Amazon), 512GB ($220 on Amazon), 1TB (as reviewed—$350 on Amazon), and 2TB ($660 on Amazon)). That’s not outrageously priced by any means considering the prices of top-notch NVMe SSDs. My test unit came with a 1TB WD Black SN750 inside—a very capable SSD (read our review). Fledging normally ships the populated models with its own Phison E12 model, which Macworld says is a very fast SSD, but slows during long transfers.

You can also buy the unpopulated enclosure for $65 and add your own NVMe SSD. If you have one lying around, that’s super-handy.

m1ulrzg Fledging

This Fledging image shows the contents of the box and nicely illustrates the diminutive stature of the Shell.

I was impressed with the solid construction of the 4 x 1.3 x 0.6-inch thick Shell. It’s hefty enough that it could easily be used as a throwing weapon if someone’s trying to heist your goods. Opinions vary, but I like heft. It’s reassuring in the hand and easy to find in the pocket.

Removing the tiny screws using the thoughtfully and wisely provided screwdriver revealed high-grade tapping (the creation of the hole with threading) and quality internals as well. There’s a single M.2 slot, and add get this—an actual fan inside.

Color me surprised, and impressed. The fan kicked in once during testing and it moves a lot more air that I would’ve thought possible from something so tiny. One of my complaints about sealed units is that they run pretty hot under heavy use. You could easily do video editing from the Shell without fear of overheating or thermal throttling (reducing performance when overheating is imminent).

tzlgcgcw Fledging

This image from Fledging illustrates the difference a fan can make in thermals. Most SSDs will throttle down if too much heat is sensed.

The Shell uses a Type-C connector and comes with two cables: Type-C to Type-C, and a Type-C to Type-A for older computers.


The performance of the Shell will vary from computer to computer, especially as some older implementations of USB 3.1 Gen 2 were lacking in the performance department. And as always, there was some disparity between the benchmarks and real-world performance.

Our tests were done with an Ablecomm x4 PCIe USB 3.1 Gen 2 adapter card on the PC, with the drive reformatted to NTFS instead of the default exFAT. exFAT is as fast with large files as NTFS, but is considerably slower with small file writes. Expect slower performance if you leave the Shell (dark purple) formatted that way.

CrystalDiskMark 6 measured the Shell/WD Black SN750’s performance as nearly twice that of the SATA-based competition.

fledging usb cdm 6 IDG

Synthetic benchmarks like CrystalDiskMark 6 showed a clear advantage for the Shell over other USB 3.1 Gen 2 SSDs we’ve tested. Yay NVMe. Longer bars are better.

While the seek times (shown below) weren’t up to NVMe-over-PCIe standards, they were clearly better than that of the SATA-based competition.

fledging usb as ssd seek IDG

Faster seeking means finding those little files and operating system transactions will be quicker with the Shell USB. Shorter bars are better.

Real world copy tests also showed a clear advantage for the Shell USB 3.1 over other SATA-based drives. However, at no point did copies proceed a much faster than 600MBps, so don’t expect the 1GBps transfers that the synthetic benchmarks hint at.

fledging usb 48gb IDG

The Fledging Shell USB with its WD Black SN750 inside was clearly superior to the SATA-based competition in every copy test. Shorter bars are better.

As Fledging is primarily a Mac vendor, we also ran Blackmagic’s Disk Speed, with similar results to the Windows-based synthetic benchmarks.

screen shot 2019 05 26 at 10.02.51 am IDG

The Shell will obviously work with Macs as well. Note that these tests were run with the drive formatted to HFS+, not with exFAT as the drive is sold.

If you want to write to the Shell using both Windows PCs and Macs, leave it formatted to exFAT or perhaps visit Paragon Software for Mac Toolbox.

As you’ve seen, NVMe adds a nice little performance boost to the USB 3.1 mix. However, it’s not doing the WD SN750 justice. You might do just as well with a cheaper x2 PCIe NVMe SSD. Also, just because you have a Type-C USB port, doesn’t mean you have USB 3.1 Gen 2. If you have one of the common 3.x Gen 1 ports, you’ll derive little or no performance benefit from the Shell over SATA-based drives.

Super solid value

Other NVMe to USB 3.1 Gen 2 adapters can be had for a bit less, but Fledging's Shell is so well thought-out and constructed, I don’t really care. It’s best of breed, and the company is also easily reachable for tech support should you have issues. Not something you can say about all your eBay and Amazon vendors.

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At a Glance
  • If you want the best possible speed from your external USB 3.1 gen 2 storage, then the Fledging Shell delivers. It's solidly constructed and despite its diminutive size, fan-cooled, which makes it suitable for intensive operations.


    • Uses fast NVMe M.2 SSDs
    • Small but solidly constructed
    • Fan-cooled for heavy usage


    • USB 3.1 10Gbps is still a limiting factor
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