Now used by most of the countries of the world, it is based on a unit of length called the meter (m) and a unit of mass called the kilogram (kg).
(it; is based; on a unit of length) (a unit of length; called; the meter) (a unit of mass; called; the kilogram)
it a unit of length a unit of mass
is based called called
on a unit of length
the meter
the kilogram