Sticker Transponder Holder.

These are plastic transponder holders that you slide in and out to pay for your tolls. You can put this on your windshield instead of the sticker because then you can't move the sticker from car to car but you can actually move the box from car to car. They have RDIF blocking technology so it doesn't charge your transponder when it's closed. The transponder sticker goes on the back side on the smooth side.