Ash catchers are a relatively new piece of smoking technology that can certainly improve many intricate water bongs. They are for two main purposes: to keep your main bong free of ash and to also add an additional layer of smoke percolation. Ash catchers come in various designs and sizes, but they typically look like mini bongs. They have filters that trap much of the ash and debris that would otherwise end up in your pipe's water chamber or stuck to the inside surfaces of your bong. Those that have percolators will pull the smoke through water to cleanse and diffuse the smoke for a smoother hit. Consider this an extra filter that will make the smoke produced by your pipe or bong easier to inhale. Your ash catcher will attach to your water pipe underneath the bowl or on the downstem. You want to put a small amount of water in the reservoir, but make sure not to put so much that it splashes into the bowl. When you take a hit, your inhale will do the work of pulling the smoke through the water to filter out ash and debris before it proceeds through the chambers of your pipe or bong. While some low-quality ash catchers can add to the drag and make it harder to get a solid hit, the best models from respectable brands won't noticeably interfere with your hit.