The Bear-Loc’s unique patented design is comprised of a rod and liners enclosed in a sleeve which forms an interference fit with the outside diameter of the rod. This interference provides a positive mechanical connection to lock the rod in any phase of the stroke. As soon as hydraulic pressure is applied, the sleeve expands radially, removing the interference and creating enough clearance for the rod to be stroked with minimal resistance. Simply remove hydraulic pressure and the Bear-Loc locks automatically.