The K9 Roof Rack Platform is comprised of a series of aluminum-extruded slats that run front to back. Each one of these slats has 2 slots where you can mount equipment. Made from non-rusting stainless steel, the 6mm or 8mm Tie Down Rings provide ultimate versatility for securing your gear to your K9 Roof Rack System. Simply insert the Tie Down Ring into any slot and slide it to the location required for your customized configuration. You can loosen and slide the ring to any location along the slate and tighten in place with a quick twist. To remove, simply twist in the other direction. This item is for (1) ring.