The Aero-Flex Universal Kit replaces a standard trimmer’s monofilament line with a unique four-line blade cutting system. The line blades, which are made of high-strength copolymers, can last up to 50 times longer than traditional nylon monofilament line. The aerodynamically engineered cutters are tough and durable enough to slice through grass, heavy weeds and vines that string lines can’t even begin to cut.