UGREEN40Gbps M.2 NVMe Enclosure with Cooling Fan, Anti-Drop SSD Enclosure for MacBook, Aluminum M.2 Enclosure Support M/B+M Key Size 2280/2260/2242/2230 Compatible with Thunderbolt 3/4/USB4/3.2/3.1

I started off with the Acasis Thunderbolt 4 enclosure. I can confirm that the Acasis unit does indeed have a Thunderbolt 4 compatible board, and the UGreen does not. However, my testing didn't show a huge difference in speeds, at least not enough to justify the trade off in thermals.The Acasis unit got VERY hot. The included thermal pad is not thick enough to reach the top aluminum plate, and I assume they do this as the Acasis seems to be geared more towards swapping NVME's regularly, vs the UGreen which seems to be geared toward installing once, and that NVME living in the enclosure long term (tools vs tool-less).The operational temp for most NVME SSD's is technically 30*C-72*C (86*F-161*F). In the Acasis, even at idle, I would clock the enclosure up at 120*F, and the drive with the top plate removed at 123*F. Under a blackmagic stress test, I could easily get the drive up to 155*F and enclosure up to 162*F.While that is within the margin of safety, and the enclosure is obviously dissipating heat as it was hotter than the drive itself, that was just too close to max temps for my comfort and I really think long term that the drive would not live very long.Now on to the UGreen. The design is MUCH better. The fan does do something. It doesn't pass air over the SSD itself, it moves air from under the SSD and over the enclosures main board. The big difference is the UGreen has a solid copper to plate, and the included thermal pad is thick enough that on a standard NVME drive it brings the height up to the height of the rest of the enclosure (you can see it in photo 2) and the NVME makes DIRECT contact with the copper plate.The temperature readings I took were after running blackmagic 5GB stress test for 10 minutes straight. The second photo at 92.3F is of the lower end of the NVME, the 108*F is the upper end. The memory modules themselves were in the 92-95*F area, well within my comfort zone.Overall, I'm much more happy with this unit over the Acasis. I think the Acasis could work if you went and got a thicker thermal pad, but I love the aesthetics of the UGreen, and in my use case, this is a drive that will always live in the enclosure, so having a screw to keep it installed is actually a pro for me. I skipped the included rubber wrap as NVME's aren't going to be damaged by shock or vibration, and I don't care if the enclosure anodizing gets scratched.Blackmagic test results done on a Macbook with thunderbolt 4 capabilities, although it is falling back to USB 3.4 due to the controller in the UGreen not supporting Thunderbolt 4. Still plenty fast for me, and way faster than any off the shelf external SSD offering.

Easy to pop SSD in and out. Fast reliable speeds

Performance is amazing compared with the Thunderbolt 5 version, HOWEVER I was not able to screw down with my NVME WD_BLACK 4TB SN850X NVMe Internal Gaming SSD Solid State Drive - Gen4 PCIe, M.2 2280. I spent a frustrating 45 minutes and think the screws are too short. Fortunately I was able to use the screw from the Thunderbolt 5 version UGREEN 80Gbps M.2 NVMe SSD Enclosure with Cooling Fan, Compatible with Thunderbolt 5/4/3/USB 4 M-Key/(M&B) Key 8TB NVMe 2280 SSD I also purchased. The printed instructions in the box have no value and I was not pointed to a Web Page or YouTube (advise if I am wrong about this). I did just email UGreen re: the screw issue. I am thinking enclosures WITHOUT screws are much better (as screws can also be lost).

40Gpbs is 5,000MB/s, so I was expecting speeds in that realm.My M.2 drive is a Samsung 990 PRO supposedly capable of speeds up to 7,000MB/s, so that's not the bottleneck here, nor is my computer, a MacBook Pro M4 Max with Thunderbolt 5/USB 4 with nothing else plugged into that thunderbolt bus.With the provided foot-long USB cable, 984MB/s write and 934MB/s read.With a 2.5-foot Thunderbolt cable from Apple, 3,519MB/s write and 3,377MB/s read.Screenshots below. Underperforming, hence the 3/5 stars, the case is nice and easy to install. It's heavy but I don't care about that, heat sinks are made of metal and metal is heavy. It's not great that the fan on this enclosure is louder than I ever hear my fan get on my MacBook Pro and yet the MBP runs at double the speeds (7,000MB/s) plus has the M4 Max chip generating even more heat than the SSD...

Buena calidad su lectura es rapidisima

Using it with an M1 Max MacBook Pro.I bought two and loaded one with 4TB NvME SSD and the other with a 1TB, both 3x4 PCIE, from Crucial.The design is okay, I don’t love the silicon bumper but it’s easy enough to remove. The material is dense enough to pickup a fair amount of heat from the SSD.The fan is audible, but not obnoxiously so.With the 4TB, using the included USB-C cable, I did a full Time Machine backup to the 4TB, about 1TB in total; I should have assumed something was wrong because the backup failed 4 times I the process (Time Machine can recover from a failed backup).When I try to restore the backup to the computer, the transfer makes it about 500GB in and the enclosure randomly disconnects.I tried several different cables and it failed consistently in the same way.I was eventually able to complete a transfer of the backup file to another USB/SATA SSD but only by using a cable that connected at 20Gbps—I verified in System Profiler.There seems to be an issue with the enclosure connecting at 40Gbps, as all of the failures occurred under this condition. Perhaps there is more heat generated at the higher speed?Also, the fan only seems to take care of the connectivity chipset, it doesn’t cool the SSD.One star because the disconnects are absolutely unacceptable.