@Dallas Joseph- Kline really has two basic sizes of boxcars. The smaller one, the one I mostly collect as it is about the same size as the Marx "deluxe" cars (those with sliding doors) , is about 8" in length (body length). The company often refers to this smaller size as "0-27 Freights". The larger size, which I believe represents a far larger number of Kline cars as they were the most recent cars, is about the size of Lionel at 9 1/6" . The larger ones also have the more complex and colorful livery at least in general.
They are fun and easy (and usually inexpensive) to collect...Good Luck Dallas
Best Wishes
Don