Faria Beede Instruments Chesapeake Rudder Angle Indicator Gauge SS 2" Black. These gauges use single or dual rudder angle indicators as a sender to give a visual display of rudder position to a gauge mounted in the boat dashboard. The senders work by measuring the angle of the rudder or rudders and converting that to a level where 180 ohms equals starboard 95 ohms is the mid point and 10 ohms displays port on the rudder indicator.Hole Size:2 inches in diameter Features of Faria Beede Instruments 2" Rudder Angle Indicator 2" - Hole size: 2.0625" (53mm) High quality marine-grade material Display: White Designed for quick and simple installation Package Contents: Faria Beede Instruments 2" Rudder Angle Indicator Faria Beede Instruments 13725: Chesapeake Rudder Angle Indicator Gauge SS 2" Black