This is one of those MUST HAVE mods IF you own the PREMIUM or LE edition of Sterns Ghostbusters PinBall Machine.
Prevents balls from launching off the back center ramp. Allows balls to roll and keeps balls on track and not hitting your walls or glass.
Easy installation. Takes 5 minutes. Protect your machine and other plastics. Worth it in the long run.

Ghostbusters Pinball Premium/LE Airball Deflector CLEAR - Stern Pinball