Adjustable shock 12 adjustment settings (resistance cylinder) used on Precor models: 723E stepper and some rowers. Overall length 21", Holes 20" center to center. NOTE: These are not PRECOR orginal shocks as those are no longer available ... some modificate will have to be done to make them fit a Precor. If you are using this on a 723E, you might have to re-use your original top bushings in the shock.