There are 16 Vents and 8 fans that make up this vent and fan passenger car detail kit to provide your N Scale passengers with recirculated air in the passenger car of your choice! There are two types of four fans each, open blade, pre-air conditioning and covered for post air conditioning. Each car is specific and different- these wer add on's during each railroads betterment projects over time. Prototype photos of your specific car is crucial to locating the fans and vents correctly.
For a fantastic database of passenger cars based on specific railroads, see Jerry's Passenger Car Photo Index at http://passcarphotos.info/