they are injection molded hard plasitc with diamond plate surface .. I was worried about the clanking noise too.. but i went and saw some floors already done and realized there is no problem, but he suggested I put down the fabric just for peace of mind.. Once the tiles are all linked together its very heavy and makes no sound or moves.. I'm very happy with them. They can custom match your car color too, or do logos.. I'm having a 5foot Z logo done to replace the tiles in the center of the room
The wife thinks I'm nuts !!!