The issues spans across several of our parts. Many of the prints just state "Masticated Rubber" but the product shortage is on the Natural Rubber. Our supply base has told us that due to the environmental reasons there simply aren't as many natural rubber sources and they continue to be hand to mouth on suppling us. I want to see if other people are using a specific synthetic rubber for applications like mud flaps and such rather than trying to start from stratch and determine that myself. I'm still waiting for the complete list, but items include mud-flaps, air flow stopping flaps, etc.