<p>A valve for use in a pipette gun for selectively providing different ranges of flow rates through a pipette cooperating with the pipette gun. The valve has a predetermined number of discrete settings, each of which provides a range of fluid flow rates between zero and a different maximum flow rate. The operator controls the flow rate by depressing the gun trigger a selected distance. To change the flow rate setting, the operator simply rotates the gun trigger to a desired setting. The present valve also eliminates the "piston effect" of prior art valve elements by isolating the pipette chamber while the valve element operably slides in and out of engagement with a port thereby connecting the pipette with a fluid source either under pressure or at a vacuum.</p>
