d'oh I got "fin" style one.. and I am using it in line with stock radiator cooler... I don't see how you can use it parallel to radiator cooler, unless you make some T fittings... I think the question most people ask is whether to install the cooler before or after the radiator cooler. Before is good when you live in really cold climate and you want the fluid to warm alittle bit after being cooled in the aftermarket cooler... After is good when you want maximum cooling during towing or hot weather....I don't think there is a need to have more then one transmission cooler.. after all you can get a real heavy duty one, the one they use on tow trucks, but that is not even necessary... btw too many coolers would block air flow to the radiator.