Kevlar belts have tensile cords. They provide better shock and impact resistance than steel or other materials. Kevlar also has a higher tensile modulus (lower stretch) than other tensile cord types, so Kevlar-reinforced belts experience less elongation over time. These are the second highest quality belts (behind Aramid) on the market and have the longest lifespan. These are suitable for all machines and the heavier applications are no problem for these belts.