Hi-Temps are built from recycled vulcanized rubber, with a 2inch (50mm) steel insert. As with most crumbed rubber bumper plates the manufacturing process can create some small imperfections, these imperfections are normal, and does not affect the performance of the plates.
Hi-Temp Bumper plates are built to withstand more drops than traditional bumper plates.
Hi-Temp bumper plates are also softer when dropped, i.e. have more bounce, therefore reducing the impact on your olympic bar or your floor.