Don't get caught without a spare mag in the field. Fill out your kit with extra mags for your Open Chamber PDW or M4. This magazine is specially designed for the WE Open Chamber (a.k.a. Open Bolt) designed PDW, SCAR, ASC and M4 and WILL NOT work with the older (closed bolt) AWSS model PDW or M4. This magazine is a real steel capacity magazine and features a "blank-fire" mode which disables the bolt top function. The "blank-fire" mode is ideal for Military and Law Enforcement training.