step 72 of lower case 60 and annular wall 84 of lower adapter 80 top support ring 100 landing nipple 110 flow tube assembly 130 and lower support rings 150 and 160 comprise inner housing 170 the substantially annular passage between inner housing 170 and outer housing 90 created by support rings 100 132 150 and 160 of inner housing 170 is hereinafter referenced by numeral 180 referring again to fig1 a 1d locking mandrel 190 is shown in position locked into landing nipple 110 locking mandrel 190 as shown is an otis 34 type r 34 locking mandrel produced by otis engineering corporation of dallas tex and is the preferred locking mandrel to use with the landing nipple configuration of choice however other locking mandrels known in the art may be employed such as the otis 34 type x 34 with a suitably configured landing nipple or landing nipples and locking mandrels manufactured by other companies and in use in the industry locking mandrel 190 comprises fishing neck 192 at its top end having annular recess 193 on its interior with annular shoulder 191 thereabove and annular shoulder 195 therebelow below fishing neck 192 on the exterior of locking mandrel 190 is dog case 194 of cylindrical configuration dog case 194 having a plurality of sets of longitudinal spring retainer apertures 196 spring expansion slots 198 and dog recesses 200 substantially evenly spaced about the circumference thereof dog case 194 is secured to mandrel case 202 at threads 201 mandrel case 202 extends upward at 204 inside of dog case 194 to the edge of annular shoulder 195 extension 204 having at least one relief.