Abstract: An adjustable socket provides continuous sizing from a minimum opening to a maximum opening to accommodate differently sized nut structures. The socket includes a socket body having a head portion and a pair of longitudinal wing portions separated by a channel region defined by a slideway region and a keyway region. A pair of jaw members are provided, each having a slide element received in the keyway region for transverse reciprocal movement and a jaw element projecting longitudinally of its slide element and received in the slideway region. When mounted, the jaw elements have facing interior work faces and oppositely facing, exterior cam surfaces. The wing portions are externally threaded and threadably receive a collar. Biasing springs apply restorative force tending to separate the jaw elements to open the region between the work faces.