An adjustable socket having first and second jaw members having manually selectable sizes. An exterior drive unit and a moveable inner driver unit each having serrated interlocking teeth are positioned to either engage during wrenching, or to be disengaged for socket size manual adjustments. The opposing first and second jaw members are forced by axial rotation of a spiral cam element located on the open top end of the outer drive unit to move laterally, inward or outward, when a user pulls the inner driver unit in a first direction and rotates the inner drive unit such that the first and second jaw members are positioned to engage a selected fastener head.