U.3

https://en.wikipedia.org/wiki/NVM_Express#U.3_(SFF-8639)

U.3 is built on the U.2 spec and uses the same SFF-8639 connector. It is a 'tri-mode' standard, combining SAS, SATA and NVMe support into a single controller. U.3 can also support hot-swap between the different drives where firmware support is available.

Compatibility: U.3 drives are still backward compatible with U.2, but U.2 drives are not compatible with U.3 hosts.

See SFF-8639

keywords

NVMe NVM Express PCIe