The metal barrel is especially designed to accommodate two special cotton filter disks. Looking into the large end of the barrel, you will see a stainless-steel screen about three quarter inch inside. This screen serves as a particle filter and support for the filter disks. It is pretty much maintenance free, but can be removed/replaced as needed. Remove it by unscrewing mouthpiece, insert the pick tool into the barrel and gently push the screen out. To replace the screen, place it atop barrel’s large end opening. Gently and evenly press it into the barrel. Using the pick tool or end of something like a Sharpie marker, push it down onto the ridge around bottom of the chamber. Use the pick tool’s curved end to lightly seat it evenly around the ridge. There are two packs of round cotton filter disks in your kit, one White, one Green. If you intend to use a Terpene flavor, apply to the inner most green disk. This provides the optimal position for inhaled smoke to be infused with the Terpenes. The white filter goes next. Its function is to filter the smoke and slow it down as it passes through. As can be seen in this Before and After filter comparison photo, the Ultra filter system works very well. We believe it is the best cannabis filter system on the market. Its effectiveness provides a cleaner, smoother, and healthier smoke without diminishing flavor.