The lower, compression section of the belt is made of highly fiber reinforced, oil and heat resistant, engineered synthetic rubber compound, specifically compounded for excellent wear resistance, cool running, flexibility and has been proven through thousands of hours of testing. The rubber directly surrounding the tensile member cables is also fiber reinforced and compounded for great adhesion to the tensile member cords. The top fabric is a specially woven, synthetic-natural fiber blend. The notches are engineered to allow the belts to have superior flexibility characteristics on smaller and larger diameter pulleys.