These disks come with an adhesive on the bottom that you use to affix to a flat surface in your vehicle. The other side of the mount is a smooth plastic that will allow you to attache the suction cup mount that came with your Garmin vehicle unit. This will keep the suction cup off the windshield and on your dash. Garmin 2-Pack of Large Dashboard Disks with Adhesive bottoms, for Streetpilot C Series and Quest Series units.