The choke tube table above shows the diameters and constrictions you can expect for choke tubes and shotgun barrels for Mossberg 12-gauge shotguns compared to common fixed choke shotgun gauges. Mossberg shotguns have two different choke systems. Early models are compatible with Winchester, Browning Invector & Mossberg 500 style threads, while newer 835/935 shotguns have their own thread styles.
Knowing the diameter of a choke tube is important in order to identify choke tube constriction. The tighter the choke tube, the more constriction it has and the less constriction, the more open a choke will be.
Choke sizes are classified by both their measurement (to a thousand of an inch) and by a special naming system. Choke measurements range from open chokes of around 0.735 to 0.770, to more restrictive chokes of around 0.600 to 0.680. Choke tubes are also classified by a naming structure that includes (from open to tight) cylinder, skeet, improved skeet, improved cylinder, light modified, modified, improved modified, light full, full, extra full, and turkey.
For choke sizes of other gauges and brands, see this chart.
Mossberg Choke Tube Markings
Markings on choke tubes come in a wide range of variations, but their meaning across the spectrum is largely the same. Manufacturers can use a notching/serration system, color coded, alpha naming scheme, and color banding to indicate the diameter of the choke tube. This is done for quick verification without having to remove the choke from the gun in most cases.