The rubber backing pads appear to be solid rubber, but actually each pad contains a metal block in the rubber pad.

The metal blocks reduce the rubber content in the pad and provide additional structural rigidity and stiffness.

The metal blocks act as "heat sinks"  in the pads, "pulling" heat away from the outer layer of the rubber.

• This reduces the heat build-up in the rubber during operation and extends the life of the rubber pad.