Water pipe down stems are integral parts of your water pipe. It’s the tube that connects your bowl to your water pipe, and without it, you really cannot use the full potential of your water pipe. Smoke will float at water’s surface and will not diffuse through the water for filtration. In effect, your water pipe will be an oversized, expensive dry pipe. Some water pipes have the option of allowing you to make a replacement of the down stem and so you can choose from the various shapes and sizes of down stems.
Few more considerations have to be made with regards to your water pipe's joint- male or female, the joint's diameter size- 10mm, 14mm or 18mm, the length of the down stem- enough to reach inside the water pipe without touching the bottom of the water chamber. And then you are ready to pick the Sloppy Hippo down stem most suitable to your equipment!