A precooler or ashcatcher is a gadget which for a small amount of money lets you upgrade your bong and smoke experience to the next level. Its function is to catch most parts of the ashes and tar so that the bong doesn't get nearly as dirty as normally. If you've ever cleaned larger bongs you know that it's not a piece of cake, which makes the precooler a desirable addition for the smoker. Additionally the smoke is filtered and cooled even further for a smoother smoke experience with lighter smoke and less throat irritation. Some models are also equipped with a percolator for top-class filtration. If you like smoking bong a precooler is essential!