Snap 4 is Apple MagSafe® compatible, nano-adhesive assisted. It takes more deliberate effort to remove than typical MagSafe® accessories because you can use other MagSafe® accessories on top of it and we don't want it coming off! The magnets inside your iPhone just aren't strong enough to keep Snap 4 on your phone if you stick it to a fridge or car mount.
P.S. it's reusable adhesive! Just run water over it, let it air dry, and it reactivates like magic.