These are stainless steel (rustproof) magnets used by fishermen in their downriggers. There are lots of applications for a device that will uncouple like these at about eight pounds pull. Split rings are provided for ease of attachment of a rope (line if you're on a boat). We sent a quantity to one of those three letter agencies for some kinda spook operation. Let your imagination fun free and your purse too; order several. These are great or folks who carry a mess of keys, the few most often used could be coupled to the rest of the wad with one of these....jailers on your gift list should definitely get one of these on the next special occasion.