The top rotor is a brand-new unit. The two lower rotors are problematic discs removed from two separate vehicles. It’s often not visually evident the rotors are degraded. However, you may find pad imprint marks where an overheated pad was held to a rotor after a long, hard stop, leaving visible pad material on the surface. Rotor thickness variation of as little as 0.001 inches can result in brake shudder.