Bong Joint Sizes Explained: 10mm vs 14mm vs 18mm, Male vs Female
A bong joint is the ground-glass connection point where your bowl, downstem, or banger attaches to the piece. Joints come in three standardized sizes — 10mm, 14mm, and 18mm — and two genders, male and female. Get those two facts about your glass right and every accessory in the industry either fits it or can be adapted to fit it.
The Three Sizes
10mm — the small one, found mostly on mini rigs and pocket-size dab rigs. About the width of a pencil.
14mm — the most common size in glass, standard on most beakers and rigs. Roughly the diameter of a AA battery.
18mm — the big-bore option on larger bongs, moving more air for bigger hits. About the width of a US quarter.
There is no 12mm or 16mm — if a joint looks between sizes, it's a 14mm.
Male vs Female, in One Paragraph
A male joint inserts into something; a female joint is inserted into. If your bowl slides into the bong, the bong's joint is female and the bowl is male — that's the standard beaker setup. If an accessory slips over a glass arm, that arm is male and your accessory needs to be female. Name the gender of the piece you're buying, not the piece you own.
How to Measure Your Joint
- Take out the bowl or banger.
- Measure across the widest part of the male taper (or the inner opening of the female joint).
- Match to the closest of 10 / 14 / 18mm — ground joints are tapered, so your measurement lands near the size, not on it.
No calipers? A dime is just under 18mm — if it nearly covers the female opening, that's an 18mm joint. If the opening looks noticeably smaller than a dime, it's 14mm.
Angles: 45° vs 90°
Joints also come off the piece at an angle — 90° (straight up, most bongs) or 45° (most dab rigs). This matters for ash catchers, which are built for a specific angle so they sit level. Match the angle or your water pours out sideways.
When Sizes Don't Match: Adapters
Wrong-size banger for your rig? Favorite 14mm bowl but an 18mm bong? A glass adapter converts one joint size or gender to another for $5 — no new glass needed. An adapter is named by its own two ends: a "14mm male to 18mm female" adapter plugs its 14mm male end into your accessory situation and offers an 18mm female opening on the other side.
Our glass adapter collection covers every combination we make, with a full conversion table for figuring out which one bridges your exact mismatch.
Cheat Sheet: What Size Is My Gear?
- Most AFM beakers: 14mm female joint, 14mm male bowl
- Our 9mm heavy beakers and 18" pieces: many run 18mm — check the product spec
- Most dab rigs: 14mm female, 45°, taking a 14mm male banger
- Mini rigs: often 10mm
- Bowls, downstems and bangers all list joint size and gender in the product name
Joint Size FAQ
Are joint sizes universal across brands?
Yes. 10/14/18mm ground joints are industry-standard — an AFM bowl fits any brand's 14mm female bong.
Can I use a 14mm bowl in an 18mm bong?
Not directly — it'll fall through. A 14mm-to-18mm adapter makes it fit perfectly.
What size downstem do I need?
Match the bong's joint size, then measure the length from the joint to about half an inch off the beaker floor. Our downstem guide walks through it.
Bowl sizes vs joint sizes — same thing?
The bowl's joint must match your bong's joint; the bowl's capacity is separate. More in our bowl size guide.