A slider and a downstem are often found in smoking pipes, especially Water Pipes or "bongs."

A slider, also known as a bowl slide or bowl piece, is part of a pipe that holds the smoking material, typically made of glass or metal. The slider is inserted into the downstem of a water pipe, allowing smoke to be drawn through the water and into the mouthpiece. Sliders come in various sizes and shapes and can be either male or female, depending on the design of the downstem. A downstem is a tube-shaped component that connects the bowl slide to the water chamber of a water pipe. It is typically made of glass or silicone and can be either fixed or removable depending on the design of the water pipe. The downstem acts as a diffuser, breaking up the smoke into smaller bubbles as it passes through the water, which helps to cool and filter the smoke before it reaches the mouthpiece.

The combination of a slider and a downstem is a critical component of a water pipe. It creates a vacuum-like effect that draws smoke through the water and into the mouthpiece, providing a cooler and smoother smoking experience. Using a slider and downstem also allows for customization of the smoking experience, as different types of slides and downstems can be used to adjust the amount and intensity of smoke drawn through the water.