Choke tube markings are a series of lines, notches, letters, or numbers that help identify the size of a choke tube. Choke tubes with 3 lines usually appear on the top of the choke tube and it can be confusing if you haven’t seen it before.
3 lines = MODIFIED CHOKE. Lines or notches indicate the size or constriction of the choke tube. A Benelli choke tube with 3 lines (III) is a modified choke. Beretta shotguns that use Mobil chokes will also show 3 lines to indicate modified.
Browning choke tube markings are slightly different, and 3 lines means Improved Cylinder Lead or Modified Steel. The line markings on a choke tube can be found etched into the top edge of the choke.
What does 3 lines on a choke tube mean?
3 lines on a choke tube means the diameter of the choke is Modified. For Benelli and Beretta shotguns using the Mobil choke system, three lines means modified. For Browning shotguns with Invector series chokes, three lines means Improved Cylinder Lead or Modified Steel.
Modified diameters differ based on shotgun brand and choke system. Below is a chart showing the diameter of modified chokes by brand.
| Type | Modified Diameter (inch) |
| Beretta/Benelli Mobil | 0.701 |
| Benelli Crio | 0.702 |
| Beretta Optima Plus | 0.707 |
| Benelli Super Sport | 0.702 |
| Beretta Optima | 0.707 |
| Browning Invector | 0.702 |
| Invector Plus | 0.715 |
| Remington | 0.702 |
More Choke Tube Markings
There are over 30 different choke tube markings used for choke identification. Below are the most common markings. Please click the links below to see what each choke tube marking means.
Why are lines used on choke tubes?
Choke tube lines are notches that are gouged into the choke to identify the choke size without needing to remove it from the shotgun. Lines on choke tubes feature 5 standard choke sizes including Full, Improved Modified, Modified, Improved Cylinder, and Cylinder.
The lines on most chokes are marked at the top edge of the choke (furthest away from the barrel) and are deep gouges that can’t be easily removed. Choke tube lines appear as I, II, III, IIII, and V.
Chokes with notches or lines on them are most common with flush factory chokes. Because these chokes sit even with the barrel when installed, it would be impossible to identify choke size without lines or markings other than having to remove the choke entirely.
Additionally, writing on a choke tube can wear off with time, especially with heavy use. The choke diameter may not be clearly legible or even visible on some older chokes. Markings such as lines and notches cannot be easily removed, and will remain for the life of the choke.
What if a choke tube doesn’t have any lines?
Some aftermarket choke tubes with customized choke sizes do not have choke lines. The diameter of the choke is typically etched onto the side of the choke instead.
Subsequently, most factory choke tubes do have choke tube lines which adhere to the manufacturers marking guidelines. Popular Browning, Benelli, and Beretta choke tube markings are listed below. Consult the manufacturers website if you are unsure of what choke markings mean.
In some cases, a choke tube will have no identifiable features. Please consult a reputable gunsmith to determine sizing and choke system compatibility before using.
Browning Choke Tube Markings and Lines
I – Full Lead or Steel
II – Modified Lead, Improved Modified Steel
III – Improved Cylinder Lead, Modified Steel
IIII – Skeet Lead, Light Modified Steel
None – Cylinder Lead, Improved Cylinder Steel
Benelli Choke Tube Markings and Lines
I – Full
II – Improved Modified
III – Modified
IIII – Improved Cylinder
V – Cylinder
Beretta Choke Tube Markings and Lines
I – Full
II – Improved Modified
III – Modified
IIII – Improved Cylinder
V – Cylinder
One line on a choke tube is always the tightest constriction for that brand of choke. It denotes a Full choke. 2 lines on a choke tube range between Light Full and Improved Modified and are slightly more open than chokes with one line.
3 lines are universally Modified chokes with steel shot and four lines are Improved Cylinder or Skeet. Some manufacturers use stars or dots instead on lines, but the premise remains the same.
Bottom Line: 3 Lines Means Modified Choke
3 lines on a choke tube means that the choke is Modified in size. A Modified choke tube is the middle ground in diameter between Cylinder and Full. Modified choke diameter ranges between 0.701″ and 0.715″ for 12 gauge shotguns.
Modified choke tubes with 3 notches work best at medium ranges up to 40 yards for ducks, geese, dove, and upland game. Lines on a choke tube can be found etched into the top of the choke tube.
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Related
- Complete Guide to Identifying Choke Tube Sizes
- Choke Tube Diameter and Constriction Table
- What do the numbers mean on a choke tube?
- Ultimate Guide to Shotgun Pellet Sizes
- What does 3 lines on a choke tube mean?
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