We use only InnerACT^TM 660 coils  Because  InnerACT^TM innersprings are assembled in alternating right-turn and left-turn coil construction, the coils act in tandem when compressed, neutralizing the tendency to shift or transfer motion in one direction. This creates a perfectly balanced sleep surface that helps to eliminate partner disturbance.  InnerACT^TM  innersprings are designed without special lacing wire that runs parallel to the body to prevent sleepers rolling together in the center of the bed. This feature, combined with alternating right-turn and left-turn coil construction, provides a perfectly balanced innerspring. Additionally, InnerACT^TM innersprings are spaced more closely together in the center to provide support where two thirds of a sleeper's body weight is concentrated.  The center density is 12% more firm to deliver the correct, firm sleeping posture for the torso and lower back. The head and foot areas have fewer, less dense springs to provide gentle comfort and support for head, neck and legs.