A honeycomb disc is a very simple style of perc, found exclusively in water pipes. The disc is a round, flat piece of glass with several holes pushed through it using a tungsten rod. Because the holes are made while the glass is hot, their edges are smooth and unlikely to accumulate tar or clog easily. Honeycomb discs break the smoke stream into several smaller streams and force each of them into close quarters with the pipe's water, filtering the smoke and removing plant debris.