Abstract: A qualitative indication of the pressure in a pneumatic tire is provided by a sliding marker in a sleeve. The marker moves in a chamber formed by a hollow lens closing one end of the sleeve and a diaphragm within the sleeve. A spring forces the marker toward the diaphragm and air pressure from the tire is applied to the opposite side of the diaphragm from the marker. A pressure above a predetermined amount is indicated by the end of the marker substantially filling the hollow lens and a pressure below the predetermined amount is indicated by the end of the marker withdrawing into the sleeve.