is a resilient elastomer generally prepared from the milky sap, or latex, of the rubber tree (hevea brasilensis). Natural rubber possesses a degree of tack (adhesive properties) not inherent in most synthetic rubbers. It may be used unblended in large tires for construction and agricultural equipment and airplanes, where low rolling resistance and low heat buildup are of greater importance than wear resistance. In the manufacture of tires for highway vehicles, natural rubber may be added to synthetic rubber to provide the necessary tack.