The Dust Shield is a 6-3/4 inch, black plastic part, used to prevent dust or debris fouling the wheel or axle. It attaches inside of the wheel around the axle. Installation is rated as "Easy" and will require a wrench. If broken, damaged, or worn due to fatigue, you will see visable damage and you may have debris getting caught in the axle. If broken, replace it. Refer to your make, model and diagram to make sure you're choosing the right part. This part comes individually sold.