It's a long piece of glass used as a connector between a bowl and the chamber. The downstem helps to attract pressure, allowing you to pass through the long cup-shaped glass as you breathe in, and acts as a connector between the bowl and the body of the tube.

The underside of the downstem is fitted with a diffuser to expand the flue gas and provide a smoother impact force.The internal cut diffuser lower stem is a perfect replacement or backup for your bong accessories.The diffuser lower stem is made of clear glass and has multiple slits that separate the bubbling smoke, increasing the surface area and making the impact more pronounced.