A small cap that covers the opening of a banger's bucket. Smoke Cartel's definition is a cap that "covers your banger's opening to control airflow and trap heat".

What size carb cap fits a 25 mm banger?

One whose listing says it fits 25 mm bangers. Here, the Wigwag Maria top ball cap lists 25 to 30 mm bangers and the two-tone bubble trap cap lists 25 to 35 mm.

Does the joint size matter for a carb cap?

No. A 14 mm joint is where the banger meets the rig. The cap sits on the bucket, so the bucket's width is the number that decides it.

Carb cap sizes: matching a cap to the bucket

Carb caps in stock whose listing states a bucket fit. Updated November 8, 2026.
Cap	Type	Fits buckets	Price
2.5 in Wigwag Maria Top Ball Carb Cap	Ball	25 to 30 mm buckets	$16.49
2 in Two-Tone Bubble Trap Carb Cap	Bubble trap	25 to 35 mm buckets	$18.99

These caps say which bucket sizes they fit. Most caps don't, and those aren't in the table.

The bucket decides, not the joint

A cap sits on the rim of the bucket, so the bucket's width is the number that matters. Smoke Cartel's caps page puts it this way: a rig's 14 mm joint "refers to the connection between the banger and the rig, not the opening the cap covers".

The cap rests on the rim. The bucket's width, not the joint, decides whether it fits.

Outside or inside: what "25 mm" means

Shops don't agree. QuartzBanger.com and Thick Ass Glass size a bucket from outer wall to outer wall. DankGeek's cap table calls the same 20, 25 and 30 mm figures the banger's inside diameter. Smoke Cartel says to measure across the outside edge, and AFM says the inner diameter of the opening is what matters.

So a bare "25 mm" can mean either, and a bucket size on this site is printed the way its listing gives it.

What other shops publish for a 25 mm bucket

These are other shops' own figures, not measurements of the caps here. They measure different things, which is why they can't be lined up into one rule:

Source	How it reads "25 mm"	The figure it gives, and what that measures
DankGeek's help center	the banger's inside diameter	22 to 25 mm: the cap, across its outside
QuartzBanger.com, a bell spinner cap sold for 25 mm buckets	outer wall to outer wall	31 mm: the cap, across its outside; 14 mm: the part of the cap that goes into the bucket
Croia Glass	a standard 25 mm banger	about 21 to 22 mm: the banger's opening, across the inside

That spread is why a cap's stated fit and a banger's stated bucket size are worth reading side by side before you order. The Fit Index has both.

Bangers here that give a bucket size

Bangers in stock whose listing states the bucket width. Updated November 8, 2026.
Banger	Bucket size, as listed	Joints	Price
Quartz Enail Banger	19 mm	14 mm male 90°	$22.99
3 in Tower Slurper Set with Etch Pillar & Dichro Marble	25 mm	14 mm male 90°	$39.99

The inch size in a cap's name

Most caps here are named by their overall size: 1.5 in, 2 in, 2.5 in, 3 in. That's how big the cap is, not the bucket it fits, so a 2 in cap isn't a cap for a 2 in bucket.

Caps that come with their banger

Some kits come with their cap. The crusher kits come with a matching cap and two terp pearls, the 120 mm competition set comes with a pillar and cap, and the slurper and tower sets come with their own marbles or caps. The banger types guide lists what's in each box.