Mine came with none both sides, pretty sure that is what they intended, but not positive.

Mine came with none on either but they sent some for that with the airball kit. I put mine on because there is enough other metal in the machine to tear up the balls already. I did run into a problem though on the right side the post was too close to the shooter lane wall and with the rubber on there it trapped the ball so I had to cut that side of the rubber flat. I also left the rubber off of the adjustable plastic post which still allows for monster side drains.