Swivel Chair Replacement Parts
Knee Pivot Mechanisms (about)

have the pivot pin located at the front of the mechanism rather than somewhat centered. This results in a more comfortable ride and also reduces or eliminates leg lift up while tilting backwards. (The forward placed pivot pin acts similar to a door hinge or clam shell.)

Usually, a knee pivot mechanism is mounted just behind the front seat rail for best results (also called a "waterfall"), but can be mounted in other areas too but then may not give the same result.

Knee pivot mechanisms always use a shorter gas cylinder than other type mechanisms as the "arm" holding the cylinder is always extended downward several inches as seen below in extreme right.