Beretta APX Grip Frame it's sold with two additional back straps: thin and large size.
Unique modular chassis system allows replacement, reconfiguration, size tailoring, including:
Different color grip frames
Customization of the frame without destroying the gun (stippling)
Ability to easily customize your APX; modifications like ‘stippling’ become less risky thanks to an easily-interchangeable frame. The break-down of the gun in its basic subcomponents also allows users to maintain their APX more easily.
for download the full APX Owner Manual (34 MB)