Magazine carriers come in a number of different configurations and are designed as a way to carry additional pistol magazines or speedloaders (for revolvers). They are typically designed to carry either one (called a single carrier) or two (called a double carrier) magazines.
Carriers attach to the belt through various methods, including:
Belt slots - This variation rides on the belt, and requires that the belt be threaded through either one or two belt slots.
Clip-On – Much like a clip-on IWB holster, the clip-on models feature a metal clip that attaches over the belt. The clip-on model is popular as it’s easy to put on or take off.
Snap-on – The snap-on style features a belt slot or slots that can be snapped over the belt. Not quite as easy as the clip-on model to put on, the snap-on model is still easier and quicker on or off compared to the traditional belt model.
Some models are designed with a built-in retention in the form of friction, while others use a tension screw for retention adjustments.