To clarify a point from our earlier FASTmag coverage, the Gen III will not stack with mil-spec PALS-style attachments. The snaps are too thick to fit through the slot but other FASTmags as well as MALICE clips fit fine.
In the pictures you see the standard Gen II FASTmag (Left) compared to a belt-style Gen III (Right). There are two styles of Gen III, the belt-style as well as a standard PALS compatible version with the ears to tuck under an upper row of PALS to enhance stability. The belt-style has a removable bar that slides along the loops to accommodate various width belts.
Down East changed from the mil-spec MOLLE attaching system to a proprietary synthetic. Also, please notice that they have improved the security of the FASTmag to the point where they feel they could omit the bungie strap from the design.