I voted for HER Car Magnet (bumper sticker)

These are bumper sticker size but are magnetic so you won't be applying a sticker to your paint job.

The front side is made with highly durable and weatherproof vinyl so that your magnet stays pristine even when left under direct sunlight.

.: Materials: white vinyl with black magnetic backing
.: White base and matte finish
.: All-weather durable
.: Please note: white base might show through design (especially dark designs)