This is a professional, high flow thermostat manufactured by AC Delco.
Opens at 195 degrees
Diameter measures 2-1/8"
Fits all GM makes, models and engine sizes listed below:
Buick 1967-1993
Cadillac 1965-1995
Chevrolet 1963-1997
Oldsmobile 1958-1993
Pontiac 1941-1993