What is a drop down?

A drop-down is a specific type of downstem that is angled downward on the outside of the bong's main body. This design allows the bowl/cone to be attached further away from the mouthpiece, which can be more convenient for users.

The purpose of this type of drop-down stem is to create a more comfortable and ergonomic smoking experience, as it can help keep the heat source (the bowl/cone) farther away from the user's face while still allowing them to inhale comfortably.