Fireball Classic has 3 mushroom bumpers on the play field. These are small ‘passive’ pop bumpers. No coil attached, and are simply hooked up to a switch below the play field. The yellow cap sits just high enough so the ball gets under it and lifts it up. That causes the switch below the play field to close. I had never seen them before, so was curious to pull one a part to see what it was made up of. Plus, there was one missing on my play field, so was going to have to track the parts down.