If you own a Duramax and you don't live under a rock you've most likely heard of the famous Mike L transmission cooler. It has been and remains the best Allison transmission drop in cooler on the market to date. This will help keep the temps in check on your stock or built Allison 1000 far better than the inadequate factory cooler. It's not uncommon to see a 20 degree decrease in return cooler return temps compared to stock and some of the copies and knock offs on the market. This cooler is not available anywhere but here and it is not the same cooler as some other previously California now Arizona based companies claim theirs to be.