nUUIDs are quite big – 16 octets.
nThey can be self-allocated on a transient basis that guarantees uniqueness up to AD 3400, with allocations of up to 10 million per second.
nThey can also be allocated for permanent identification.
nRegistration is not required, but reduces probable uniqueness from 99% certain to 100% certain.
nCan be used as ASN.1 OID components.