Armatac emailed me a photo of their new prototype Quad-Mag. The Quad-Mag is a 5.56x45mm quad stack magazine with a 60 round capacity.

It differentiates itself from other quadstack magazines by having two separate feed channels. When the first feed channel is empty, it switches to the other channel. Essentially its two 30 round magazines in a small package. This reduces jamming in the part of the magazine where quad stacks are reduced to a duel stack for feeding.