CO2 Cartridge Sizes Explained: 8g vs 12g vs 16g vs 45g (And Threaded vs Non-Threaded)
May 12, 2026
Buying CO2 cartridges for the first time is confusing: sizes from 8 to 88 grams, threaded and non-threaded necks, and packaging that rarely tells you what fits your tool. Here’s the short version we give customers on the phone.
The quick answer
| Size | Threaded? | Most common use |
|---|---|---|
| 8g | No | Soda siphons, BB/pellet guns |
| 12g | No | Bike inflators, airsoft, life jacket re-arm kits |
| 16g | Both | Bike tires (threaded inflators), HVAC drain guns |
| 25g | Threaded | Larger bike/MTB tires, big inflation jobs |
| 45g | Threaded | High-volume drain clearing, fat bike tires |
Rule of thumb: if your tool screws onto the cartridge, you need threaded (3/8”-24 UNF). If the cartridge drops into a sleeve and gets pierced when you tighten the cap, you need non-threaded.
Threaded vs non-threaded: how to tell
Look at the neck of a cartridge you’ve used before:
- Threaded cartridges have visible screw threads below the tip. The tool seals against a gasket as you screw it in. Drain guns, most modern bike inflators, and re-arm kits use these.
- Non-threaded cartridges have a smooth neck. The piercing pin in the tool punctures the seal. Classic BB guns and older inflators use these.
They are not interchangeable — forcing a non-threaded cartridge into a threaded head wastes gas and can be dangerous.
Which size for HVAC drain guns?
The industry standard for clearing AC condensate lines is the 16g threaded cartridge. One 16g cartridge delivers enough pressure to clear a typical 3/8”–1” drain line in one or two shots. Service techs doing multiple calls a day usually buy 16g threaded in 25 or 100 packs. For long runs or stubborn clogs, a 45g threaded cartridge gives roughly three times the gas per shot.
Which size for bike tires?
- Road bike (up to 28mm tires): 16g fills to ~100+ PSI
- Gravel/cyclocross: 16g or 20g
- MTB 29er: 20–25g
- Fat bike: 25–45g
Most modern inflator heads are threaded; check yours before ordering. 12g non-threaded still fits many budget inflators and all standard life-jacket re-arm kits.
FAQ
Do CO2 cartridges expire? The gas doesn’t go bad. Stored dry and out of the sun, sealed cartridges last for decades — the limiting factor is rust on the steel body.
Are food-grade and standard CO2 different? Our cartridges are filled with food-grade CO2. For beverage use (kegerators, soda), always confirm food-grade — it’s filtered for purity and filled on clean lines.
Can I fly with CO2 cartridges? TSA allows up to four small CO2 cartridges in checked baggage for life vests in the US, but rules vary by airline. Don’t put them in carry-on.
How should I dispose of empty cartridges? Empty steel cartridges are recyclable with scrap metal. Make sure they’re fully discharged first.
Still unsure? Email us a photo of your tool and we’ll match the cartridge — or request bulk pricing if you go through cases.