This genuine, original equipment (OEM) retaining nut holds the Water Temperature Sender into the Thermostat Housing. Be sure to check the condition of your old nut prior to replacing the water temperature sender, as they often become corroded and need replacement.
Datsun 240Z, 260Z, 280Z, 280ZX
Datsun S30, S130
1970, 1971, 1972, 1973, 1974, 1975, 1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983