parts rules question

Hi all–I have a question regarding the rules that cover certain parts–the rules specify that “no traction device” can be made of metal. The intention of the rule seems to be that teams not make drive wheels with cleats, spikes, etc. which would tear up the carpet. We have 2 drive wheels (unmodified) and 4 ball casters which support the corners of the robot. The ball casters are made of metal. Can anyone define whether we are in violation of the rules?

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