A hollow magnet shaped like a large ring, with a tiny detachable neodymium cube magnet, in a longer rubbery wand that makes it easier to hold. This magnet creates a sort of wide circular black hole effect when held over the nail, but it can be held at different angles and distances over the nail to adjust the shape and size of that circular effect.

It can be used to activate any magnetic polishes on your nails while the polish is still wet. Hover the wand for at least 60 seconds over the nail while the polish dries, or paint your nail directly on top of the magnet while the polish sets.

You only need to magnetise the final coat of the polish, as well as magnetise it the same way after applying top coat, it is not necessary to magnetise the initial coat of the polish.

Swatches shown use Creeping Lies over the thumb, courtesy of @pretty.fluffing.ugly.