This is just as lukie games describes. Dust covers for your NES Games.
most people may think these are redundant, but this is an item you need to buy. these protect the sensetive reading heads of your games from dust and grim. and considering that lukie games ships the games you just bought clean the heads of the games, better to keep em clean.
some have writing on em in a blue permanete marker. if you are like me and dont want anything on your cases, go grab a container of Metyl Alcohol or a Mr. Clean Magic eraser and give em a clean up. fair warning though, if cleaning a "Nintendo" dust cover, dont touch the red lettering of Nintendo, these chemicals will take that off too.
you should really buy some of these.