automatic transmision cooler... keeps that thing cool for better performance/longer life.... and like it was said, doesn't have to be in race conditions... atx build a lot of heat and the cooler they are the longer they last...
basicly what he said. kinda like a radiator for the atx fluid. you have one stock but its on the bottom of the 190-210 degree radiator. aux cooler helps cool the fluid better.
