The outside fabric wrap is treated with highly oil and heat resistant, engineered synthetic rubber, specifically compounded for superior wear resistance, proven through thousands of hours of customer use to be durable and dependable. The helically wound tensile cords are specially manufactured with twisted, heat and chemically set, polyester material. The body rubber is a highly engineered synthetic rubber compound, specially compounded for cool running, crack resistance, and excellent bonding to the outside fabric and tensile cords.