Abstract: An apparatus for setting a bottom tool comprising a valve body having its lower end portion connected to a bottom tool and an upper end portion connected to a source of fluid under pressure, an elongated bore within the valve body, a valve member slidable within the bore and having a piston exposed to the fluid under pressure movable from a first position whereby the application of the fluid under predetermined pressure imparts longitudinal movement to the valve member to a second position whereby the valve member transmits the force of the fluid under pressure to the bottom tool, seals provided on said piston for preventing the fluid exerting pressure against said piston from flowing through the bore of said valve, and a packing medium provided in the bore intermediate the piston and the lower end portion of the valve body.