Quoted from Shannyman:From my understanding they were put there to keep the plastics from warping from heat of bulbs. This came from a guy who has been repairing pinballs for over 25 years not me. Ive always reused them when doing playfields.
</blockquoteThat would scratch the heck out of the plastic, around slings I could see. Some places it is so balls do not get stuck behind the rubber.