Concentric cable is generally used by DNOs to supply most modern cutouts, but it’s use is not exclusive to DNOs.
There are two different types of concentric cable.
Their selection / use depends on the supply type.
This is a DNO cutout supplied by a straight concentric cable.
(This is a TN-C-S supply)
This is a DNO cutout supplied by a split concentric cable.
(This is a TN-S supply)
Some pictures of split concentric kindly provided by Lectrician
The cable with the sheath stripped back
After its prepared; the earth is sleeved as two separate bits to keep it tidy
25mm² Split concentric terminated in a consumer unit through a bush and locknut