This replaces the floppy drive cover on your dell optiplex sff pc. It may fit others but I only know for sure that it fits the sff optiplex with a slim cd rom drive (optiplex 780, 745, etc). It allows more airflow into your pc and these little furnaces need all the help they can get to stay cool.
If you don't have a heated print bed then it may curl when removing it from the printer. I used a hair dryer to heat it slightly and bend it back flat. It fits exactly like the factory piece.