Short answer: buy the gas tube named for your barrel's gas system. Makers list a pistol tube at about 6.6 to 6.75 inches, carbine at 9.75 to 9.8, mid-length at 11.75, and rifle at 15.125 to 15.25. Intermediate is not standard: Wilson Combat's is 13.25 inches. Stainless and Melonite (nitrided) tubes both work; the tube is held in the gas block by a small roll pin.
Gas tube lengths
| Gas system | Gas port (approx.) | Listed tube length | Examples |
|---|---|---|---|
| Pistol | About 4 in | 6.625 to 6.75 in | Aero 6 3/4, Battle Arms 6.6875, Guntec 6.625 |
| Carbine | About 7 in | 9.75 to 9.8 in | Aero 9 3/4, Riflespeed 9.79, Battle Arms 9.8 |
| Mid-length | About 9 in | 11.75 in | Aero, Battle Arms, Guntec |
| Intermediate | About 10 in | Not standard | Wilson Combat 13.25 |
| Rifle | About 12 in | 15.125 to 15.25 in | Battle Arms 15.125, Aero 15 1/4, Guntec 15.25 |
Lengths are from maker listings (Aero Precision's via Brownells), read October 2026. Small differences between makers are normal; what matters is the system name. See the gas system length chart to find your barrel's system.
Intermediate and extended tubes
Intermediate gas sits between mid-length and rifle, but it is not standardized. Wilson Combat describes its 13.25 inch tube as proprietary, so match the tube to the barrel maker's spec. White Oak Armament sells extended rifle-length tubes at 16.160 and 17.160 inches; use one only when your barrel maker calls for it.
Stainless vs Melonite
Most tubes are stainless steel. Some makers, including Aero and Battle Arms Development, also sell Melonite (a nitride finish), which is black and so less visible through a handguard. Both carry gas the same way.
The roll pin
A small roll pin through a cross hole in the gas block passes through the front of the tube. It holds the tube in place and keeps the hole in the tube lined up with the gas block's passage. Replacement pins cost about a dollar.
Installing a gas tube
- Remove the handguard so you can reach the gas block (see handguard length for your gas system).
- Slide the tube into the gas block so its pin hole lines up with the block's cross hole, then drive in the roll pin with a punch.
- Install the gas block on the barrel with the tube passing through the barrel nut into the upper receiver (see gas block sizes).
- Check that the bolt carrier's gas key slides over the tube smoothly before you install the handguard.
Gas tubes, with today's prices
Lowest price across the stores we track:
Battle Arms Development pistol gas tube, 6.6875 in, Melonite
Pros
- Pistol length
- Black Melonite finish
Cons
- Pistol gas only
Pistol
Aero Precision carbine gas tube, 9.75 in, stainless
Pros
- Carbine length
- Stainless steel
Cons
- Carbine gas only
Carbine
Spikes Tactical carbine gas tube, Melonite
Pros
- Carbine length
- Melonite finish
Cons
- Carbine gas only
Carbine, black
CMMG mid-length gas tube, stainless
Pros
- Mid-length
- Stainless steel
Cons
- Mid-length gas only
Mid-length
Wilson Combat intermediate-length gas tube
Pros
- 13.25 in, for Wilson intermediate gas
Cons
- Intermediate is not standard; check your barrel
Intermediate
Guntec USA rifle gas tube, 15.25 in, stainless
Pros
- Rifle length
- Stainless steel
Cons
- Rifle gas only
Rifle
Luth-AR gas tube roll pin
Pros
- Replacement pin for the gas block
Cons
- Check your block's pin size
Roll pin
Compare all gas blocks and tubes, or plan the build in the AR-15 builder. For the theory, read gas systems explained.
Frequently asked questions
How long is a mid-length gas tube?
Makers list mid-length tubes at 11.75 inches.
How long is a carbine gas tube?
About 9.75 to 9.8 inches, depending on the maker.
How long is a rifle-length gas tube?
About 15.125 to 15.25 inches.
Can I use a carbine gas tube on a mid-length barrel?
No. The tube must match the gas system; a short tube will not reach the upper receiver correctly.
Is a stainless or Melonite gas tube better?
Both work. Melonite is black and less visible through the handguard; stainless is the common default.
Does a gas tube need a roll pin?
Yes, a standard tube is pinned into the gas block with a small roll pin that holds it and lines up its gas hole.
