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.

This little enclosure is really great, probably the best on the market right now. See below a quick summary of Pros and Cons:Pros:- Small. Although I bought it to have it on my desk, I could easily travel with it.- Rock solid performance (see attached image). Best of all, **performance is maintained even when using longer cables**. That is not always the case with other enclosures (e.g. Satechi). I ran tests using the included cable and a 3.3-ft thunderbolt 4 compatible cable. Transfer numbers were basically the same.- Built like a tank. It feels like a solid block of aluminum, even the internals are metallic.- It is provided with an extremely silent fan. It is temperature controlled, so it only kicks in when needed.- Includes a removable silicone sleeve.- Adequate price.Cons:- Included cable, although it works, it's a bit short and feels somewhat cheap. A braided one would've been great.- Since closing the lid requires a short sliding motion, the friction against the thermal pad makes it a bit hard to close. This is really a minor thing.I didn't know Ugreen made this type of devices. I'll keep them in mind next time I'm on the market for a similar product.

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...

The performance is quite good. It has good heat conducting material on both sides. Also has cooling fan. As mentioned by other customers, fan get louder on heavy use.

This compact NVMe enclosure is a great option for those looking for a reliable and efficient storage solution. It’s designed to fit in small spaces and is compatible with Mac mini computers. The installation process is straightforward and hassle-free, and the enclosure comes with a protective rubberized cover that makes it easy to transport.One downside of this enclosure is that it can get quite warm under heavy workloads, which triggers the fan to kick in and cool it down. The fan noise is relatively low and automatically switches off when the temperature drops below a certain threshold. The cable that comes with the enclosure is quite short and stiff, so if you need to place the drive in a specific location, you’ll need to purchase a different cable.Despite these minor issues, the drive has been working flawlessly so far. I’ve been using it with my Mac mini for several days without any problems, and I don't usually turn off the Mac at nigh. This is a great alternative to expensive Mac storage options, and it offers a reliable and efficient way to store your data.