This bong percolator 18 has an arm, with two cuts in each to maximize production of bubbles. Adding a little water filter will offer extra other than already incorporates the diffuser.
This diffuser is finished with a small perforated disk, which break the flow of smoke or steam from the bowl, passing it through the water as a lot of bubbles, this will hydrate and cool it, and will retain other unwanted particles, which will remain in the water.
For easy emptying, it also has a carb hole to be dropped when inhaling and emptying the entire tube at once. A rubber stopper is included for easy cleaning or you can empty it in the "American" way, by lifting the bowl.