Car rosary is hung on your vehicle's rear view mirror and its main purpose is to remind you of your Catholic faith. Since the beads are so close to you, you can always take it off the mirror and pray while driving. In a sense the auto rosary provides spiritual protection for you and the occupants of your car. Any rosary can be displayed on your mirror, there is no specific one made for this purpose. Some use regular size 5 decade rosary while others prefer shorter, one-decade rosary beads. In the end its just a of string of beads, what you do with it matters. Have your auto rosary blessed and keep this special object close to when you need to pray and contemplate the life of Jesus Christ.