The Miata's stock temperature gauge is not accurate at telling you how hot your car is running, just like most OEM water temperature gauges on the gauge cluster. In order to accurately tell what the coolant temperature is, a dedicated water temperature gauge is a must. This becomes even more important for owners who take their cars to the track often and not cause irreversible engine damage.
 
Maruha's water temperature sensor adapter allows you to mount a sensor by the thermostat. The  mount is tapped for a 1/8PT pitch sensor.
 
This adapter will work with the Maruha 78°C Thermostat on the 1.8L engines.