Can I ask what you use for the back? A metal clip on to the spike or a rubbery stopper? I need to know because when I put pins on my purse the only stay if they're securely fastened.

They have rubber backs. I've found them more reliable than butterfly clasps, but for the best security I recommend buying a cheap little pack of locking backs off eBay so you can add them your whole collection. Or if you don't mind permanence my mum superglues the rubber backs onto her bags lol.