embodiment the generally upward facing shoulder 55 inclines slightly upward at an angle relative to the axis of the bore 30 of the inner wellhead member 29 as illustrated in fig3 in this embodiment the centralizer overpull ring 45 is a split ring having an annular band 57 with a plurality of resilient finger members 59 extending upward and outwardly from the annular band 57 at an angle u03b8 fig1 from the axis of the bore 30 of the inner wellhead member 29 to form a collet like member in this embodiment there are six finger members 59 positioned around the diameter of the annular band 57 each finger 59 being separated from another by a slot 60 the diameter of the centralizer overpull ring 45 decreases from the annular band 57 to the finger members 59 thereby forming a generally upward facing shoulder 61 the upward facing shoulder 61 is substantially geometrically complimentary to the downward facing shoulder 53 on the inner wellhead 29 fig1 as illustrated in fig1 in this embodiment the centralizer overpull ring 45 is connected to the inner wellhead member 29 by a plurality of fasteners 63 that extend through a plurality of apertures 64 in the annular band 57 portion.