orientations without deviating from the principles of the present invention apparatus 100 as representatively illustrated in fig2 a and 2b is specially adapted for use within a service tool string not shown which is suspended from tubing extending to the earth 39 s surface the tubing being longitudinally disposed within protective casing in a subterranean wellbore 102 in fig2 a and 2b the wellbore 102 is external to the apparatus 100 the service tool string is typically inserted through a packer 103 shown in phantom during a fracturing job a pressurized abrasive slurry is then pumped through the tubing and into the service tool string tubular upper connector 104 and lower connector 106 permit interconnection of the apparatus 100 into the service tool string accordingly upper portion 108 of upper connector 104 is connected to the service tool string above the apparatus 100 and lower portion 110 of lower connector 106 is connected to the remainder of the service tool string extending below the apparatus 100 note that illustratively cut surface 112 of fig2 a is continuous with the same cut surface 112 of fig2 b axial flow passage 114 extends longitudinally i e axially downward from the upper portion 108 of upper connector 104 through the.