Examples are xenon tetrafluoride where the inversion center is at the Xe atom, and benzene (C6H6) where the inversion center is at the center of the ring. Rotation-reflection axis: an axis around which a rotation by 360 ∘ n {\displaystyle {\tfrac {360^{\circ }}{n}}} , followed by a reflection in a plane perpendicular to it, leaves the molecule unchanged. Also called an n-fold improper rotation axis, it is abbreviated Sn.