It was a magnet for a telescopic retriever tool mechanics would use. He had a couple in the box, either as extra's or of varying magnetisms. I already put it in my glovebox and agreed to buy him a replacement. I tried with my own retriever tool previously with no luck but I don't know if I was trying it the right way. I think the cap looks nice and is a preliminary deterent but the real security is in the locking lug.