Downstem

ˈdau̇n-stem | Noun

A long piece glass that serves as a connector between the bowl and the body of a bong or water pipe. The downstem facilitates a suction pressure that draws the smoke down through the mouthpiece as you inhale. They can be removable or fixed to the glass piece. Downstems are often equipped with diffusers that aerate the smoke and provide a smoother hit.

 

That downstem on my bong looks like a mini water tube slide.

 

She chose a downstem customized with a diffuser to attach to her ceramic bong.