This is I believe GM’s highest capacity engine fan. It’s a twenty inch diameter Thermostatically controlled fan that can be used on most all of the small and large block engines prior to the newer LS type. This came off a 3/4 ton GM van and is in good condition with a working thermostatic control to aid in improving mileage and lessening drag for increased performance when maximum cooling isn’t needed. It moves an awful lot of air.