Smart point at the center of mass.
If the mass properties are automatically
calculated, this will be the same
as the origin of the marker below.
These origins can be different
for user defined mass properties.

Internal marker that defines the
origin and orientation of the inertia
values. If the mass properties are
automatically generated, the origin
will be the same as the mass_center
above and the orientation will be the
principle axes.

The mass of the link

The products of inertia of the link
in the following order: Ixx, Ixy,
Ixz, Iyy, Iyz, Iyz

TRUE if overriding default mass
properties with user defined values.