OWC 1TB Express 1M2 NVMe Thunderbolt (USB-C) USB4 Ultra Fast External SSD with Aluminum Enclosure for Heatsink

Whilst expensive, it absolutely delivers. I have a good consistent speed with no speed throttling due to thermal constraints.Everything else is as it states in the specI used this on a M4 mini and can confirm 3200 as quoted.

Unfortunately i bought the wrong drive size (1tb) was after a 2tb so had to return. But it looks fabulous.

There are multiple versions of this device with 1TB, 2TB, and 4TB SSDs pre-installed or you can buy a version which is an empty enclosure in which to put your own SSD. I purchased the 1TB version.This device is advertised as delivering 3000MB/s for both reads and writes when connected to an M1 (or later) iMac. Having tested the device with my own M1 iMac, I can confirm that it does achieve 3000MB/s reads, but it would only achieve slightly less than 1000Mbps write speed (see screenshot) with my iMac.If you aren't worried about the speed of data transfer, there are much much cheaper SSD enclosures available (e.g. Sabrent do a metal USB-C SSD enclosure which I bought on Amazon which is much smaller, runs much cooler and only costs about £10, but then it only delivers slightly less than 1000Mbps reads and writes).As I wasn't getting the write performance I was expecting from this OWC Express 1M2, I decided to return it. To be fair, I have seen other reviews which show this device achieving 3000 MB/s writes so perhaps I was unlucky or perhaps it is just an issue with M1 iMac compatibility.A couple of other points to note:1. The case of this device does get very hot when in use.2. The versions of this device supplied with an SSD pre-installed do not appear to be upgradeable as the case appears to be sealed with the SSD already inside. If you want to buy an OWC Express 1M2, you may be better off buying the version which is an enclosure only and putting your own SSD in it. That way you can always change the SSD if you want one with greater capacity later or you can replace the SSD if it fails without having to junk the enclosure as well.In summary, this isn't a bad device. If you are primarily interested in read speed, then this device is extremely fast. If however, like me, you have an M1 iMac and you want something that has a fast write speed as well, based on my experience of it, you may be better looking somewhere else.