passage communicates with the cavity 31 as best seen in fig1 the nozzle 19 has a flange 43 that registers with the upper counterbore of the passage 17 integral threads 45 to mate with the threads 33 of the intermediate counterbore and an upper cylindrical end 47 that engages and seals against an o ring 49 thus all fluid that flows through the passage 17 must pass through the bore of the nozzle 19 first through a convergent upper end 51 and then through a noncircular throat 53 which is hexagonal as best seen in fig3 and through a divergent lower end 55 the purpose of the hexagonal throat is to provide a means to apply torque to the nozzle 19 in a manner that minimizes size while providing excellent strength this enables the use of an allen type wrench to be inserted into the throat 53 of the nozzle to provide make up and break out torque the throat has a minimum cross sectional dimension to receive the mating wrench and a minimum length to transmit the torque of make up and break out without damage to the nozzle in the embodiment shown here the minimum cross sectional dimension meaning the distance across an opposed pair of parallel flats of the hexagon shaped throat 53 should be not less than 3 16 inch and the length of the throat should be not less than 1 4 inch the advantages of.