AutoMeter Platinum Marine Analog Speedometer, Liquid Pitot Operation, 80 MPH, 3-3/8"Aluminum casings, sealed lenses UV protected needles for fade resistance Non corrosive hardware Come with White Lights with Red removable cover 3 7 8 Outer diameter 3 3 8 hole size Require the use of a pitot style water pressure feed system for operation**Pitot pick ups sold separately. New Autometer Pitot Operated Speedometers do not include a fitting. See related items below for Pitot hose fittings.