to more firmly secure it in sealing engagement with the sealing surface 25b on the ball valve 25 in other words the total area of downwardly facing surfaces exposed to the fluid pressure above the ball valve will exceed the upwardly facing surfaces exposed to said fluid pressure proceeding downwardly from the connecting sub 32 fig2 b and 2c it will be noted that external threads 32c on the bottom end of connector sub 32 provide a connection with an intermediate part 33 of the outer tubular housing 30 this connection is sealed by an o ring 32e a threaded radial port 33b is provided in the upper end of the intermediate part 33 to permit annulus fluid pressure to enter the bore of tubular housing 30 immediately below the radial port 33b the upper portion 42 of the tubular actuating assemblage 40 is secured by threads 42c to a piston sleeve 44 piston sleeve 44 has a radially enlarged shoulder portion 44a mounting an o ring 44b in sealing engagement with the bore 33a of intermediate part 33 of outer housing 30 an annular internal shoulder 32f on connecting sub 32 mounts o ring 32g which sealingly engages the external surface 42e.