Abstract: An improved hydraulic vise jaw incorporates a fluid supply which communicates hydraulic fluid to an area behind a plurality of pistons such that the pistons are held outwardly against a part with a generally uniform force. Each piston is positioned in a piston cylinder. The piston cylinders are arranged in several columns and a supply passage connects each of the piston cylinders in an upper row and a second supply passage connects each of the piston cylinders in a lower row. A communication hole selectively connects a first piston cylinder in the top row with a second piston cylinder in the bottom row. Preferably, the communication hole connects piston cylinders which are in distinct columns. In this way, the flow of hydraulic fluid between the rows is somewhat restricted such that an equal and adequate holding force is maintained on the pistons. In another feature, a pin selectively holds the pistons within the piston cylinders such that they are prevented from moving outwardly of the body.