The rubber mat is made from conductive material. If your keys are worn out, you might want to exchange these with our replacement parts.
There are different PS4 controllers which looks to be the same. These rubber parts are suitable for controllers with motherboards JDM-001, JDM-011 und JDM-020. Not for -030 und 040. You have to open the joypad to see if you select the correct pads.