So, our Grip Tuck is a “universal holster,” and it’s made in various sizes to accommodate a rough handgun frame size.
Pistols can be classified by various attributes, but when it comes to the actual size of the gun, the industry nomenclature follows frame size+barrel length. In the broad strokes, the size of the frame combined with the length of the barrel puts the pistol in a particular size category.
In addition, the industry also includes the magazine design. You have single-stack (one vertical column of bullets) and double-stack, which is a staggered double-stack of bullets, with each round resting part of the way on the next one down.
For instance, a Beretta 92FS is a full-size double-stack pistol, and no the “FS” doesn’t stand for “full-size.” (It means “Forged Slide,” in case you’re curious.) The Smith and Wesson Bodyguard 380, meanwhile, is classified as a micro pistol.
Some guns don’t entirely fit in one class but not entirely in another. A good example is Commander-frame 1911 pistols. Some people refer to them as a compact, but they aren’t really; the barrel is usually 4.25 inches long and the grip is a full 5.5 inches tall. It’s smaller than the classic Government frame 1911, which has a 5-inch barrel, but since a Commander is almost the same size as a Glock 17, you can’t REALLY call it a compact, now can you?
Now, as it happens, the Grip Tuck Universal Holster is also sized by frame size and barrel length.
Source: Alien Gear Holsters