The state at which a circle within a larger circle within a larger circle (etc.) all have a common center. Implicit in the concept of concentricity is the perfect roundness of each circle, an important consideration in the proper running of a printing press cylinder, in which the journal, bearing steps, bore, and outside diameter of the cylinder all need to be as close to perfectly circular as possible, and have the centers of their respective diameters all meet at the same point. (See also out-of-roundness and total indicated runout.)