The six-member ring of cyclohexane can exist in various shapes known as conformational isomers, or conformers. The most stable conformers are the chairs; the least stable are the half-chairs. The hydrogen atoms in the molecule can assume two distinguishable positions: 'axial', when they are more or less perpendicular to the average plane of the ring; 'equatorial', when they lie close to the plane. When the chair flips from one conformation to the mirror image, axial hydrogens become equatorial and vice versa. .