Have a Nucleus water pipe but have broken the downstem? Get the Replacement Downstem that fits most Nucleus products! It is a 4" 18mm to 14mm clear glass downstem that has Nucleus branding on it. The downstem can hold 14mm bowls in any piece that has an 18mm joint and the necessary space in its chamber. Slits at the bottom of the Replacement Downstem diffuse your smoke for a more smooth hit.