ACASIS TBU405 vs Sabrent EC-U4TN: Which 40Gbps NVMe Enclosure?

Both of these enclosures turn a bare M.2 NVMe SSD into a fast external drive over a 40Gbps USB-C port, and both sell for well under $100. The difference is in the details that decide how fast the drive actually runs on your computer: the bridge chip inside, whether there is a fan, how the SSD goes in, and what happens when you plug into an older port. The ACASIS TBU405 is the cheaper, lighter, passively cooled option built around an Intel Thunderbolt controller. The Sabrent EC-U4TN is a tool-free, fan-cooled USB4 enclosure built on the newer ASMedia ASM2464PD chip with a higher speed claim on USB4 hosts.

Everything below comes from manufacturer spec sheets, current Amazon listings, and published coverage. Speed numbers are the makers' claims, not a lab shootout. If you want the wider field of enclosures, the Best USB4 M.2 NVMe Enclosures Under $100 in 2026 roundup covers more options; this page is a narrow head to head of exactly these two.

Quick verdict

Most people should buy the Sabrent EC-U4TN. It has the higher speed ceiling on modern USB4 laptops, a fan that helps during long copies, and a tool-free tray that makes swapping drives painless. The ACASIS TBU405 wins if you want the lowest price in this pair, a silent fanless shell, or you mainly plug into an older Thunderbolt 3 machine where its Intel controller is right at home.

Chipset and speed

Winner: Sabrent EC-U4TN on USB4 hosts; close to a tie on Thunderbolt 3/4.

The bridge chip is the part that translates between the SSD and your computer's port, so it sets the ceiling. In plain terms, a 40Gbps link is the size of the pipe, and the chip decides how much of that pipe a storage drive can actually use.

• ACASIS TBU405: ACASIS uses a dual-chip design. An Intel JHL7440 Thunderbolt 3 controller handles the 40Gbps path, and a Realtek RTL9210B handles the fallback to ordinary USB. ACASIS rates it at up to 2,805 MB/s read and 2,734 MB/s write, measured by ACASIS with a Samsung 980 series SSD on a MacBook Pro.
• Sabrent EC-U4TN: Sabrent confirms the ASMedia ASM2464PD controller, a single chip that speaks USB4 natively and talks to the SSD over PCIe 4.0 x4. Sabrent rates it at up to 3,900 MB/s on USB4 hosts and up to 2,700 MB/s on Thunderbolt 3 or 4.

Why the gap on USB4? Thunderbolt 3 controllers like the JHL7440 carry storage over a PCIe tunnel that tops out around 2,800 MB/s in practice. USB4 hosts let the ASM2464PD use more of the pipe, which is where the 3,900 MB/s claim comes from. Published reviews of ASM2464PD enclosures commonly report results above 3,000 MB/s on capable USB4 laptops, but the number moves with the host, the SSD, and the file mix. On a Thunderbolt 3 or 4 port, the two are rated within about 100 MB/s of each other, and most people will not notice that difference.

If you are not sure what your port is, the USB4 and Thunderbolt explainers cover how to tell.

Cooling and sustained writes

Winner: Sabrent EC-U4TN.

NVMe SSDs get hot when they write for minutes at a time, and when they get too hot they slow themselves down to protect the drive. That is called thermal throttling, and it matters for long video dumps, big backups, and game libraries more than for quick file copies.

The Sabrent has an integrated fan plus an aluminum body and a thermal pad. Sabrent pitches the fan specifically at keeping the drive running fast during large transfers. Owner reviews on Amazon are mixed on heat: many describe the enclosure as only warm, while some still report it running hot with certain drives. The fan does add a small source of noise.

The base TBU405 is fanless. It relies on a ribbed aluminum shell and a thermal pad to pull heat away from the SSD. That makes it silent, and for normal copies it is enough. Owner reviews also mention heat problems with very hot drives, including PCIe 5.0 SSDs, which are a poor match for any 40Gbps enclosure anyway. ACASIS sells a separate fan-cooled Pro model if you want the ACASIS approach with active cooling, but it is a different product at a different price.

Either way, the drive you pick matters as much as the shell. A cooler-running PCIe 4.0 SSD in a passive enclosure can outlast a hot drive in a fan-cooled one before throttling.

Build and tool-free install

Winner: Sabrent EC-U4TN for convenience; ACASIS TBU405 for size and weight.

The Sabrent is tool-free. You remove the top cover, drop the SSD into the slot, secure it with the built-in retainer, and close it. If you swap drives often, that saves real time and removes the tiny-screw problem.

The base TBU405 uses screws to hold the SSD and close the shell. It is a one-time job for most people, but it is slower if you rotate drives. ACASIS quotes about 97 g for this shell, and it is compact enough to disappear in a pocket. The Sabrent is longer (Amazon lists it at about 5.1 inches) because of the fan and cooling channels.

Cable matters more than it seems. Sabrent includes a 0.3 m USB4 Type-C cable rated for the full speed. For the ACASIS, the listing pictures a 40Gbps-marked USB-C cable with the enclosure; confirm the box contents on the listing before you rely on it. If you need a longer run, a short certified cable from the Best Thunderbolt 4 and USB4 Cables in 2026 guide keeps you at full speed. Long, cheap USB-C charging cables often drop you to USB 2.0 speeds.

Compatibility: Thunderbolt, USB4, USB 3.2, Mac and Windows

Winner: tie, with different strengths.

• Thunderbolt 3 and 4: Both work. The ACASIS uses an Intel Thunderbolt 3 controller, which has a long track record on Intel Macs and Thunderbolt 3 PCs. Sabrent rates its enclosure at up to 2,700 MB/s on Thunderbolt 3 or 4.
• USB4: Both connect at 40Gbps. The Sabrent's native USB4 chip is the one with the higher ceiling here. Some USB4 hosts that are not Intel based treat Thunderbolt 3 devices differently, so a Thunderbolt 3 style enclosure can behave less predictably on those machines.
• Older USB-C and USB-A ports: Both fall back to regular USB. Expect roughly 1,000 MB/s on a 10Gbps port and about half that on 5Gbps. Sabrent notes that 20Gbps USB 3.2 Gen 2x2 ports also land around 1,000 MB/s. The USB 3.2 explainer covers the naming mess.
• Mac vs Windows: Both makers list Windows and macOS support, and both are bus powered with no driver. Both listings also mention Linux, though Linux setups can need extra configuration.

A few Mac notes, phrased carefully because results vary by macOS version and drive. When either enclosure runs over its Thunderbolt or USB4 path, macOS generally sees the SSD as an NVMe drive, and features like TRIM tend to behave as they would internally. Over the plain USB fallback, the drive is handled as USB storage, where TRIM support on macOS is less predictable. Booting macOS from an external drive is possible on many Macs, but neither maker promises it for these enclosures, so treat it as a bonus rather than a reason to buy.

On Windows, ACASIS notes that slow write speeds can come from the default disk policy. Turning on write caching for the drive in Device Manager is the fix it recommends.

Drive size support and which SSD to pair

Winner: slight edge to Sabrent EC-U4TN for clearly documented fit.

Sabrent lists M-key PCIe NVMe drives in 2230, 2242, 2260, and 2280 lengths and says plainly that M.2 SATA drives are not supported. It also discourages SSDs with their own heatsinks. The ACASIS listing names 2230 through 2280 support for M-key and B+M key PCIe NVMe drives up to 8TB, also with no M.2 SATA support and a note to skip heatsink drives.

For either enclosure, a mainstream PCIe 4.0 x4 SSD is the sweet spot. A PCIe 5.0 drive will not run faster through a 40Gbps link and usually runs hotter. A DRAM-less drive is fine for most external use and often runs cooler. If you are choosing the SSD too, the Samsung 990 EVO Plus vs WD Black SN7100: Which 2TB NVMe SSD? comparison covers two good matches. The NVMe explainer covers the basics if the terms are new.

Price

Winner: ACASIS TBU405.

Recent Amazon pricing puts the ACASIS TBU405 around $70 (often marked down from about $81) and the Sabrent EC-U4TN around $90. That $20 gap buys the fan, the tool-free tray, and the higher USB4 ceiling. If your computer only has Thunderbolt 3 or 10Gbps USB-C, the speed part of that premium is mostly wasted, and the ACASIS is the better value. If you have a USB4 laptop and move big files often, the Sabrent earns its extra cost.

Who should buy which

Buy the Sabrent EC-U4TN if you have a USB4 laptop or a recent Mac, you move large video or backup files often, you swap SSDs regularly, or you want a fan helping during long writes.

Buy the ACASIS TBU405 if you want the lower price, a silent and lighter shell, you mostly connect to an older Thunderbolt 3 Mac or PC, or you will install one SSD and leave it there.

Skip both if your computer only has 5Gbps or 10Gbps USB-C and you never plan to upgrade; a cheaper 10Gbps enclosure gives the same real speed there. If you want several drives on a network instead of one in your bag, look at the Best All-Flash NVMe NAS Boxes in 2026 guide. For a factory-sealed alternative with no drive to install, see Samsung T9 vs SanDisk Extreme PRO USB4: Which Pocket SSD in 2026?. And if you also need extra ports on the road, the Best Compact USB4 Hubs for Travel in 2026 guide pairs well with either enclosure.

Bottom line

These are two good 40Gbps NVMe enclosures that win different fights. The Sabrent EC-U4TN is the overall pick: higher rated speed on USB4 hosts, a built-in fan for sustained copies, tool-free install, and a full-speed cable in the box. The ACASIS TBU405 is the value pick for Thunderbolt 3 machines and anyone who wants a silent, compact shell for about $20 less. Match the enclosure to your port first, pair it with a mainstream PCIe 4.0 SSD, then View on Amazon for whichever fits.