Typically the rubber balls were designed for pitching machines..pitching machines tear the cover and stitching off of quality leather baseballs. Any type of RIF or cushioned ball should work fine in a batting cage envirement, Your there to work on your mechanics and timeing, the only drawback is you dont get the feel for the sweetspot of your bat, (mis-hits) batting helmets "should" be mandatory for entry into a cage, and exiting a dugout,to swing... Ive seen more kids hit each other with bats than line drives. Obviously all netting and L-screens should be inspected, From some of the screens I've seen Its been a miracle more kids haven't been seriously injured from BP.