NOS Motorcraft Engine Coolant Thermostat fits 1991 Mercury Topaz 2.3L-L-4. 192F.  Over 30,000 NOS OEM parts in stock!  Ford, Motorcraft, Autolite, GM, ACDelco, Mopar and more.  Check out our site: www.connecticutclassiccarparts.com (Motorcraft Box 1)