Elite Tactical Systems or ETS designs their magazine products so that they mirror the function of their factory counterparts with some additional features. The transparent body allows the shooter to quickly determine how full or empty the magazine is and it also looks great full of 30 rounds. ETS magazines are made of a lightweight and durable polymer material tested and proven to be highly resistant to cracking or shattering or warping. Their internal springs are tested for fully loaded magazines left for extended periods of time so that you can rest assured that leaving your mags around loaded to capacity will not wear down the tension. Elite Tactical Systems magazines should lock your weapon open on empty just like the factory magazines do feed reliably and drop-free when ejected.