The modern Dresco Woods valve fits the same inner tube and rim as a Dunlop valve. The Woods valve does not have a valve tube but a small ball that is pressed down by the air pressure during inflation, thus releasing the opening. When used, the overpressure in the tyre causes the ball to rise up and close the air gap. Less pressure is needed to inflate an inner tube with a Woods valve than with a Dunlop valve. The Woods valves are delivered in sets of four.