Horus keeps it "eye" peeled on your case feeder drop tube, looking for those pesky steel cases. When it sees one, it grabs hold and hangs on so you can remove that junk to a recycling bin.
Horus is a 3d printed plastic ring that fits tightly around your case feeder drop tube. It is backed by an N42 neodymium, epoxy coated magnet. This magnet is strong enough to catch even a fully loaded, steel cased, bimetal jacketed 308 round.