These are made to stop the glare from the dot matrix display reflecting off the playfield glass. After fitting these guards you can see right into the back of the pinball machine which was previously obscured by the glare. It is quickly fitted as it slides into the same plastic channel as the playfield glass does. It is of the right height and angled so that you can still see the dot matrix display clearly. It has texture on the side facing you so that any stray light is reflected into your eyes.
If you want multiples, buy one and we'll sort it out. Here's a link for further info: http://www.wrongcrowdproductions.com/glareGuard.htm