as a composite mandrel 12 can optionally have a passage 13 that can be optionally closed with a ball landed on a seat or with a valve not shown shoulder 14 supports sealing element 16 a cone 18 has individualized tapered surfaces 20 on which a slip drag block or other retainer collectively referred to as slip 22 is guided between opposed surfaces 24 and 26 the slips 22 are each connected to a slip ring 28 that has a triangular undercut 30 when viewed in section in fig1 that extends for 360 degrees preferably the undercut is defined by surfaces 32 and 34 as better seen in fig2 the undercut 30 and lock ring 36 may be inverted from the fig2 position in which case the ribs 56 will be oriented uphole to resist differential pressure in an uphole direction lock ring 36 has an outer surface 38 that is preferably parallel to surface 32 of undercut 30 bottom surface 40 of ring 36 is contacted by surface 34 of undercut 30 during the setting process a shear pin or some other breakable member 42 allows the sealing element 16 to be compressed against a surrounding tubular that is not shown before the slips 22 are released to move up ramp surfaces 20 by the breaking of the shear pin 42 movement of ring 28.