Abstract: A mechanism for gripping an object employing a set of jaws which are adjusted to fit the size of the object by means of a limit or sizing stop device. The object is gripped by the jaws secured to the end of a stationary lower member while a movable upper member grips the opposite side of the object. A post operably supports a piston which is pivotally connected to the end of the upper member so that the piston, when moved up and down under pneumatic control, causes the jaws to move together or spread apart.