Abstract: An improved drag string unit is shown for use with well bore drill stem test tools of the type which have an inflatable packer and an integral pump. The drag spring unit has an outer drag spring housing and an inner mandrel slidably received within the drag spring housing. Ratchet surfaces associated with the outer housing and inner mandrel are positionable between an engaged position which allows the pump to be activated to pump up the packers and a disengaged position which prevents activation of the pump. Vent means are alignable between the inner mandrel and outer housing when the ratchet surfaces are disengaged allowing the packers to vent to the well bore.