Match the downstem’s outer joint to the bong and its inner joint to the bowl.
Measure twice. Order once.
Find the Right Bong Downstem
Find a replacement bong downstem that matches your joint configuration and measured length, or upgrade to a diffused design for added filtration.
Shop by fit and function
Choose Your Downstem
The outside joint fits the bong; the inside joint fits the bowl. Confirm both numbers and the usable length before ordering.
Showerhead Diffused
Multiple slits create smaller bubbles and smoother diffusion.
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Open-End
Classic direct airflow with a simple design that is easy to clean.
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Grid & Multi-Hole
Precision openings add diffusion while maintaining balanced airflow.
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Replacement Glass
Straightforward replacement options in a range of usable lengths.
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Adjustable Metal
Durable adjustable designs for compatible bongs and specialized fits.
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Silicone
Flexible, break-resistant downstems for compatible silicone pieces.
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Bong Downstems
Vendor:
Aqua Lab Technologies
14/18mm Replacement Glass Bong Downstem
Regular price $16.00 Sale price $16.00 Regular price
Vendor:
ROOR Glass
ROOR Glass 14/18mm Open-End Bong Downstem
Regular price From $40.00 Sale price From $40.00 Regular price
Vendor:
ROOR Glass
RooR Glass 18/18mm Open-End Bong Downstems
Regular price $48.00 Sale price $48.00 Regular priceGet the fit right
How to Measure a Bong Downstem
Remove the existing downstem and measure from the top lip of the ground joint to the end of the downstem. Use that measurement when selecting the replacement length.
Do not measure only the exposed section below the joint. The full usable length begins at the top lip of the ground joint.
Three measurements
Length and Joint Size
- Outside joint: The first number is the joint that enters the bong—commonly 14mm or 18mm.
- Inside joint: The second number is the opening for the bowl. A 14/18mm downstem takes a 14mm bowl and fits an 18mm bong joint.
- Downstem length: Measure from the top lip of the ground joint to the end. The end should sit underwater without touching the bong wall.
Plain English: 14/18mm means a 14mm bowl goes into an 18mm downstem that fits an 18mm bong joint.
Compatibility checklist
Check These Before You Order
Long enough to reach the water, short enough to clear the chamber wall.
Open-end for a classic draw; slits, grids, or holes for added diffusion.
Quick shopping guide
Common Downstem Length Availability
Availability changes by product and inventory. Use this chart to identify the product families most likely to carry your measured length.
| Measured length | Common product families | Typical configurations |
|---|---|---|
| 2.5–3.5 inches | Alex K, Aqua Lab replacement | 14/18mm and 18/18mm |
| 3.75–4.5 inches | Alex K, ROOR, Zob, Accurate | Replacement, slit, grid, showerhead |
| 4.75–5.5 inches | Alex K, ROOR, Accurate | Open-end and diffused |
| 5.75–6.5 inches | Alex K, ROOR, Aqua Lab | 14/18mm and 18/18mm |
| 6.75–7 inches | Zob and Alex K | Long replacement and showerhead |
Classic airflow
Open-End
A simple open tip provides direct airflow and is usually easier to clean.
More diffusion
Slit, Grid, or Multi-Hole
Additional openings break smoke into smaller bubbles. More diffusion can cool the draw but requires regular cleaning.
Built for durability
Adjustable or Silicone
Adjustable metal and flexible silicone options can reduce breakage and cover specialized fits.
Complete the connection
Related Bong Parts and Guides
Downstem Frequently Asked Questions
How do I measure a replacement bong downstem?
Measure from the top lip of the ground joint to the end of the downstem. Also confirm the outside joint size that fits the bong and the inside joint size that holds the bowl.
What does 14/18mm mean on a downstem?
The 14mm opening accepts a 14mm bowl, while the 18mm outer joint fits an 18mm bong joint.
Will any downstem fit any bong?
No. The joint sizes and usable length must match, and the tip must clear the chamber wall while reaching below the waterline.
Are diffused downstems better than open-end downstems?
Diffused styles create more bubbles and may cool the draw more. Open-end styles offer simpler airflow and cleaning.
How far should a downstem sit in the water?
The diffuser openings or tip should sit below the waterline without touching the bottom or side of the chamber.