A packer, preferably utilized for dual string operations, comprising a plurality of axially stacked body elements including, from the bottom up, a hydraulic housing, a lower cone element, an annular slip cage containing radially expansible slip elements, an upper cone element, a lower packing expander, an expandable packing element, an upper packing expander, a receptacle, and a retainer plate. All of said elements are provided with two bores equal in diameter to that of the tubing string to be run which extend entirely through the axial stack. One bore accomodates a long string mandrel and the other bore accomodates a short string mandrel conventionally connected to a short tubing string. The short string mandrel is connected at one end to the hydraulic housing and at the other end to the receptacle housing. Fluid pressure is applied to concurrently effect the downward movement of the hydraulic housing and the upward movement of the lower cone to set the packer into engagement with the conduit wall. The packer is secured in set position by one or more locking rods detachably secured to the retainer plate and extending through the axially stacked assemblage to a unidirectional ratcheting connection with the lower cone element.