How to Measure a Downstem for a Bong
Updated October 2026 · Shatter Kitchen
To measure a downstem, measure only the clear glass tube from the bottom of the frosted ground joint to the tip of the stem. At Shatter Kitchen every downstem length is listed that way, so if your old stem measures 5 inches below the joint, a 5" stem from us is the same length. No old stem? You can measure the bong itself with a pencil in a couple of minutes, and we show you how below.
What is a downstem and do you need one?
A downstem is the glass tube that runs from your bong's joint down into the water. Your bowl slide sits in the top of it, and the bottom end releases air into the water, where it gets diffused and cooled before it travels up the tube. A stem that is too short sits above the water line, and one that is too long hits the floor of the bong, so length matters.
A removable downstem only works with a female joint on the bong, because the stem has to slide down into it. Some pieces have a fixed stem built in, like the 7" Encore Bent Neck Beaker Bong with Fixed Stem, and those take a bowl slide directly with no separate stem to buy. If your bong uses a rubber grommet instead of a ground joint, our guide to glass-on-glass vs grommet bongs explains the difference.
How do you read downstem sizes like 18/14?
Downstems are labeled with two numbers. The first is the joint that fits into your bong, and the second is the joint your bowl slide fits into. Length is listed separately.
| Label | Fits into the bong | Takes a bowl slide |
|---|---|---|
| 18/14 | 18mm (18.8mm) female joint | 14mm (14.4mm) male slide |
| 18/18 | 18mm (18.8mm) female joint | 18mm (18.8mm) male slide |
| 14/14 | 14mm (14.4mm) female joint | 14mm (14.4mm) male slide |
The 18/14 is the most common combination. Our Glass Downstem 18-14 Low Profile Slit Cut Diffuser fits into an 18.8mm female joint and takes a 14.4mm male slide, in lengths from 4.0" to 6.0". If you are not sure which joint your bong has, start with how to measure a ground glass joint size. As a quick check, a 14mm joint is roughly the width of an index finger and an 18mm joint is closer to the width of a thumb.
How do you measure a downstem you already have?
This is the easiest method. Lay your current stem on a table next to a ruler.
- Find where the frosted ground joint ends and the clear glass tube begins.
- Measure from that point straight down to the very tip of the stem.
- Do not include the frosted joint in the measurement.
That number is your downstem length. If your old stem worked well, order the same length. If it sat too high or low in the water, adjust up or down from there.
How do you measure a bong for a new downstem?
If the original stem broke or never came with the piece, measure the bong itself. All you need is a pencil, a marker and a ruler.
- Insert the pencil. Slide it straight down through the female joint at the same angle a stem would sit, until it touches the bottom of the bong.
- Mark the joint. Make a mark on the pencil where it meets the bottom edge of the joint opening, where the frosted section ends inside.
- Measure. Pull the pencil out and measure from the tip to your mark.
- Leave room. Subtract about half an inch so the stem tip sits under the water without touching the floor of the bong.
Round to the nearest available length. When in doubt, measure twice. Getting the joint size right is just as important as the length, since a perfect-length stem with the wrong joint still will not fit.
Does the downstem diffuser style matter?
The tip of the stem decides how air enters the water. More openings break air into smaller bubbles, which means more surface contact with water and more cooling. More diffusion also means a bit more drag on the pull and more spots to clean.
- Open end: one opening at the bottom. Simple and easy to clean, with the least diffusion.
- Slit cut: slits around the tip split the air into smaller bubbles for a smoother pull than an open end. Slits do make the tip a little more delicate, so handle it with care.
- Showerhead or multi-arm: more openings for heavier diffusion, with more drag and more cleaning.
For a deeper look at how much diffusion is right, read diffusion: how much is too much. You can see every length and style in our downstems and ash catchers collection.
What does a low profile downstem mean?
A low profile downstem has a short, compact joint that sits close to the top of the bong's joint instead of sticking up above it. It keeps the bowl slide closer to the bong and gives the setup a cleaner look. Measure it the same way, from the bottom of the frosted joint to the tip.
What else should you check before ordering?
- Bowl slide fit: the top joint of the stem has to match your slide. Our bowls and slides collection lists joint sizes, and the Funnel Slide W/ Handle comes in several joint sizes.
- Joint size: if your bong has an 18mm joint, our 18mm joint collection shows compatible parts in one place.
- Ash catcher: adding one changes the angle and height of your slide, so plan for it. See what is an ash catcher.
Keep reading
Frequently asked questions
Where do you measure a downstem from?
Measure only the clear glass tube, from the bottom of the frosted ground joint to the tip of the stem. Do not include the joint itself. This is how every downstem length at Shatter Kitchen is listed.
What does 18/14 mean on a downstem?
The first number is the joint that fits into your bong, and the second is the joint your bowl slide fits into. An 18/14 downstem fits an 18mm female joint on the bong and takes a 14mm male slide.
How far should a downstem sit from the bottom of the bong?
The tip should sit under the water line without touching the floor of the bong. When measuring a bong with a pencil, subtracting about half an inch from the full depth is a good rule of thumb.
Can I use a downstem with a male joint bong?
No. A removable downstem needs a female joint on the bong so it can slide down inside. Male joint pieces take a female bowl directly.
What happens if my downstem is too long?
A downstem that is too long will hit the bottom of the bong and will not seat fully in the joint, which leaves a poor seal. Measure again and size down to the next available length.
Sold for legal use only. You must be 21 or older to purchase.