Abstract: In a PBR system in well bores, a retrievable landing assembly which can be set either mechanically or hydraulically has a telescopic setting sleeve and setting collar where the setting collar is interconnected to a setting tool by a first threaded nut member and a second threaded nut member. The setting tool is threadedly attached by one of the threaded nut members to the setting collar and the one threaded nut member is splined for longitudinal movement with respect to a mandrel of the setting tool while the other nut member is longitudinally and releasably splined to the setting collar and threadedly attached to the mandrel of the setting tool. The setting tool has a shiftable sleeve member which can be shifted by a pressure ball and applied pressure to shift the setting sleeve of the landing assembly into a locking position in the setting collar.