Natural Rubber (NR) is harvested as latex from Hevea rubber trees. Polyisoprene (IR) is a synthetic version of Natural Rubber. These polymers are known for having excellent elongation, rebound, and energy absorption properties.

Because it is an organic product, Natural Rubber does have more problems with consistency from lot-to-lot than most man made polymers. Individuals with Latex allergies can respond negatively to Natural Rubber. Both Natural Rubber and Polyisoprene tend to revert when used at elevated temperatures.

The operating temperature range for these polymers is -50º to 180ºF (-45º to 80º C). PAI offers compounds in a hardness range of 30 to 70 durometer. Black is the standard color, but several other colors are available.