How to measure a joint, and a downstem
Updated
All you need is a US dime, or a ruler with millimeters. It takes a minute or two.
1. Male or female
Look at the joint where the bowl goes. If it's a hole with frosted glass inside, it's female. If the frosted part sticks out, it's male. More on male and female
2. A female joint: the dime test
Lay a dime flat on the opening.
- It sits on top: it's 14 mm. The opening is 14.5 mm across and a dime is 17.91 mm.
- It drops in about 9 mm: it's 18 mm. The opening is 18.8 mm across, wider than the dime, and it narrows as it goes down, so the dime wedges about 9 mm in.
Don't use a penny. It's 19.05 mm across, too wide to go into either size, so it sits on top of both and tells you nothing.
3. A male joint: the ruler
Measure straight across the frosted part at its widest point, the end farthest from the tip.
| You measure | It's a |
|---|---|
| about 14.5 mm | 14 mm joint |
| about 18.8 mm | 18 mm joint |
4. A downstem: its length
Downstems are sold by length: the part that hangs down inside the bong. Measure your old one from the bottom of its frosted joint to the tip, and round to the nearest quarter inch. We sell clear downstems in several lengths.
Downstem joints are named with two numbers, like 18/14: the end that goes into the bong, then the end that takes the bowl. Not sure which one you need? Send us your old one's two numbers and its length, and we'll help you pick.
5. Then find the part
Once you know the size and male or female, go to the 14 mm chart or the 18 mm chart. Every bowl and ash catcher we have is there, under the joint it fits.
Questions
- Why does my 14 mm bowl measure 14.5 mm?
- The name is rounded. The real size is 14.5 mm at the widest point, and bong shops call it 14 mm.
- Can I measure a female joint with a ruler?
- Yes, straight across the inside of the opening at the very top: about 14.5 mm or 18.8 mm. The dime is easier than holding a ruler over a hole.
- What about 10 mm?
- If it measures about 10 mm, it's a 10 mm joint. Those are mostly on small dab rigs, not bongs, and we don't carry them.
Sources
The dime's size is from the US Mint. The joint widths are from ISO 383, and the way they narrow from ground glass joints. How downstems are measured and named: Thick Ass Glass's downstem size guide.