Hadn't seen that before.
I have the Element, and can't say I'd find a real use for it - unless I'd already cleaned out all my magazines and still needed to get a round or two off.
Do you like the Element? I have the Carbon and like it a lot...
With the mags that I carry, I have up to 20rds available to me. I can't think of any reason other than having "20+2" that I would actually need this. I guess from a speed perspective, it's quicker to load 1 round versus removing the mag and inserting another one.
They do look cool and I see them all the time, but I never see them being used.
The fudd method is to carry a round in every pocket. You need a quick replenishment, reach into a pocket.