and their respective end portions are in a telescoping or overlapping relationship and are connected together by cooperating internal and external threads respectively provided thereon since these types of connections are conventional they will not be described in any further detail an annular packing 86 is located between the upper end of the circulating sub 82 and a shoulder 80a formed on the packing sub 80 a plurality of annular spaced openings 82a one of which is shown extend through the sub in axial alignment with the openings 34a of the mandrel 34 the openings 16c in the housing 16 of the sliding sleeve valve 10 and with the openings 26b of the sleeve 26 in its open position an indexing sleeve 88 extends between the upper end of the cap 84 and a shoulder 82b defined by the stepped outer surface of the sub 82 the inner diameter of the sleeve 88 is slightly greater than the outer diameter of the corresponding portion of the sub 82 and the outer diameter of the sleeve is slightly less than the corresponding portion of inner diameter of the mandrel 34 to permit rotation of the sleeve for reasons to be described as shown in fig3 a plurality of slots 88a are provided in the lower portion of the sleeve 88 which receive the indexing pins 58 and a plurality of slots 88b are provided in the upper portion of the sleeve 88 the sleeve 88 also includes angled cam surfaces 88c and 88d located adjacent the slots 88a and 88b respectively for reasons to be described during downward movement of.