 BLAKE2X is itself not an instance of a hash function, and must be based on an actual BLAKE2 instance.An example of a BLAKE2X instance could be BLAKE2Xb16MiB, which would be a BLAKE2X version based on BLAKE2b producing 16,777,216-byte digests (or exactly 16 MiB, hence the name of such an instance).BLAKE2b and BLAKE2s are specified in RFC 7693.