It's just a simple clip. Those German clips work well with Fiocchi "black box" ammo -- cartridges won't fall out of the clip while loading (a common problem that we see frequently in youtube.com shooting videos). A small video shows this combo: DWM clip + Fiocchi ammo + Mauser. It's very easy to use:
http://tinypic.com/r/10glc2b/9