AC Delco 3 port vacuum switch. 1/2"-14 NPT. Ships in AC Delco box. 

This is the only replacement available for the TCS transmission controlled vacuum spark advance.

Fits the following Cadillac vehicles:
Calais 1976
Commercial Chassis 1976-79
DeVille 1976-79
Eldorado 1976-80
Fleetwood 1976-79
Seville 1976-80