Abstract: An annular pressure activated downhole tool has a housing including an outer surface, an inner surface defining a passage, an annular projection projecting into the passage from the inner surface, and an opening. A mandrel extends into the passage. The mandrel has a first end and a second end. A power spring support is detachably connected to the second end of the mandrel in the passage. A power spring is arranged about the mandrel and extends between the power spring support and the annular projection. A trigger housing is arranged in one of the mandrel and the power spring support. A trigger arranged in the trigger housing selectively engages with the inner surface. The trigger is operable to disengage from the inner surface of the housing, releasing the power spring, and shifting the mandrel along the passage when exposed to a selected annular pressure.