Gunwebsites has a close up of the US Palm Quad stacks:
EDIT to add:
Interesting that US Palm as two capacities coming out, a 30 and 45, the one pictured in my first post on them seems to be the 30 and will be around $80 and the 45 one wasn't pictured but from the video looks to be about the same length as a 30 rounder at about $100 (I wish he would have put the AK30 right up next to the prototypes so I could tell for sure). Also the US Palm rep mentioned "metal feed lips" which would be completely new for US Palm.
Honestly, the smaller one at 45 was more exciting. At about only 10 more compared to a similar size 20 round double stack metal mag, or only 15 more for one at a double stack 30, it is definitely an improvement but will the bulk be worth it if it is only 50% more ammo when there are plenty of 40 rounder double stacks out there for cheap and you will have to potentially change your pouch setups?
The short one I think will definitely have a niche for a those that run foregrips closer to the mag well (like AMD-65s) because they will give more rock in room.