Most chest rigs require you to make adjustment to the fit while the chest rig is off your body. Then you must repeatedly check the fit, remove the rig, adjust the fit, and then re-check the fit until it is adjusted to your liking. Beez Combat Systems has designed their harnesses to be adjusted while you are wearing the rig. This means that you can easily adjust the fit to adjust to layered clothing or to ride over a plate carrier.
This video shows how the adjustments work on the BCS AK-47 Low Profile Chest Rig.