Downstems Explained: What They Are & How to Measure Them Correctly
If you’ve ever ordered a replacement downstem and realized it didn’t fit, you’re not alone. Downstems are one of the most misunderstood bong parts — especially when it comes to measuring them the right way.
This guide explains what a downstem does, why it matters, and how to measure a downstem correctly (because most people do it wrong).
What Is a Downstem on a Glass Bong?
A downstem is the glass tube that connects your bowl slide to the water inside your bong. When you take a hit, smoke travels:
Bowl → Downstem → Water → Bong → You
In most beaker-style glass bongs, the downstem is removable — and it plays a huge role in:
- Airflow
- Filtration
- Smoothness
- How harsh or clean your hits feel
Even the best glass bong won’t perform properly without the right downstem.
Why the Right Downstem Matters
A properly fitted bong downstem helps:
- Break smoke into bubbles for better cooling
- Improve airflow
- Reduce harshness
- Make your bong easier to clear
Most modern setups use diffused downstems, which have slits or holes at the bottom to increase filtration. This small detail can completely change how smooth your bong hits.
The #1 Mistake People Make When Measuring a Downstem
🚫 Measuring from the very top to the very bottom.
This is the most common mistake when buying a replacement downstem.
Incorrect method:
Top of the joint → bottom of the downstem
This usually results in a downstem that’s too long, which can cause:
- Poor airflow
- The downstem hitting the base
- Cracks or breakage
How to Measure a Downstem Correctly
✅ Always measure from the bottom of the joint to the bottom of the downstem.
Here’s the correct step-by-step method:
1-Remove the downstem from your bong
2-Locate the frosted joint section
3-Start measuring at the bottom of the joint
4-Measure straight down to the tip of the downstem
That measurement is the true downstem length.
Example:
Bottom of joint → end of downstem = 4 inches
👉 You need a 4" downstem
This is the industry-standard way to measure bong downstems.
Why Downstem Length Is So Important
If a downstem is:
- Too long → it can block airflow or crack the base
- Too short → it won’t reach enough water, causing harsh hits
The correct length ensures:
✔ Proper water filtration
✔ Smooth airflow
✔ Better overall performance
Downstem Joint Sizes Explained
Most glass bongs use one of two joint sizes:
- 14mm downstem (most common)
- 18mm downstem
When buying a replacement downstem, always match:
- Joint size (14mm or 18mm)
- Correct length
- Joint angle (usually straight for beaker bongs)
Diffused vs. Non-Diffused Downstems
Diffused Downstems
- Slits or holes at the bottom
- Create more bubbles
- Smoother hits
- Better filtration
✅ Recommended for everyday use
Non-Diffused Downstems
- Straight tube
- Minimal filtration
- Stronger, harsher hits
If smoothness matters, a diffused downstem is almost always the better choice.
Quick Checklist Before Buying a Downstem
Before ordering a replacement, make sure you know:
-Your bong’s joint size
-The correct downstem length
-Whether you want diffused or non-diffused
-That the downstem sits just below the water line
Getting this right saves time, money, and frustration.
Final Thoughts
A downstem may look like a small piece of glass, but it has a massive impact on how your bong performs. Measuring it correctly ensures smoother hits, better airflow, and a perfect fit every time.
Just remember:
👉 Never measure top to bottom
👉 Always measure from the bottom of the joint
Once you know that, replacing or upgrading your downstem becomes simple.
