A central inversion, order 2, is operationally differently by dimension. The group [ ] = [2 ] represents n orthogonal mirrors in n-dimensional space, or an n-flat subspace of a higher dimensional space. The mirrors of the group [2 ] are numbered ⁠ 0 … … n − − 1 ⁠. The order of the mirrors doesn't matter in the case of an inversion. The matrix of a central inversion is ⁠ − − I ⁠, the Identity matrix with negative one on the diagonal.