Our precision-cut clear clings for the Clean Air/Pass Vehicle Decals are made from Xpel Stealth Paint Protection Film, and ship as a complete set of four (2 large, 2 small). You need these because removing the official decals (again, not included) from your car isn't (by design) easy, and leaves a nasty residue that's very difficult (and annoying) to remove. This complete set includes 2 large and 2 small decals. Each is a little larger all around than the actual decal, so it's virtually impossible for anyone to know it's there.
These have a light adhesive, so you can apply and remove these many times; if you plan on doing this, always ensure the paint is clean where you're applying them, and keep the plastic carrier sheet they arrive on for storage when they're not on the car.