Coolant Gauge Adapter Small
Small Coolant Gauge Adapter. Specifically designed for Spec Miata's, this heater hose adapter will work for any car with 5/8" heater hose. This adapter features a 1/8" NPT threaded hole, allowing the use of most popular gauge senders. Shown with an "Autometer" water Temperature sender (not included).
(page 72 in Spec Miata Construction Manual)