Which M.2 drive and which port does the ACASIS USB4 enclosure need to actually reach 40Gbps?
The 40Gbps figure looks like a property of the enclosure alone, but it is a chain: the drive, the port on your computer and the cable all have to support it. ACASIS sells this as a USB4 enclosure that is Thunderbolt-compatible, for turning an M.2 solid-state drive into an external drive you can carry. Three things are worth settling before you pay. First, the drive standard, because NVMe and SATA M.2 drives are not interchangeable, and the title does not state which one this accepts. Second, the drive length and key, since a short 2230 drive will not line up where a 2280 sits. Third, the port on your machine: an older USB 3.2 port will run the drive but nowhere near the advertised rate, and a Thunderbolt 3 host negotiates lower than a USB4 one. The cable matters as much as the rest, because a charge-only cable is a common reason people conclude the enclosure is slow. What the listing does not spell out is the supported drive length, the internal interface and the rated speed at each port type, so ask the seller before ordering. Listed at 630.88 yuan against a 1,999 yuan original, with annual sales around 2,000 units.