Downstems are simple devices that direct smoke from a bowl down to a water pipe’s main water chamber. They are made from heat resistant glass and easily slide into the correct sized joint and can be purchased in a variety of sizes to fit 10mm, 14mm, or 18mm joints and bowls. Diffused downstems often provide the first step of percolation and filtration in a bong or dab rig. Parallel slits at the bottom of a diffused downstem cause smoke to split up into different streams, increasing the surface area of the smoke as it passes through water. This cools and filters smoke to a certain degree. Some beaker and tube bongs rely solely on downstems when it comes to percolation, using the structure of the bong itself as the main method of diffusion. Look through our varieties of downstems to choose the right one for your piece.