These are the dies that go into the Crystal Snap/Button Applicator hand tool. They hold the crystal components in place and correctly lined up while you squeeze the handle to apply the crystals. This tools was designed by Swarovski for simple, hand installation of the snaps and decorative buttons. Clothing manufacturers and other professionals use a "fly press" to install the snaps, which is thousands of dollars and takes up the floor space of a dishwasher. This handy gadget can't do 400 in an hour, but is way better for home use!