Finally, a pleasant trimming experience, Uses Four (4) easy-loading, powerful, economical, strong and reliable Aero-Flex Line Blades: uniquely aerodynamic and streamlines (like an air plane wing) to recover lost drag power, save fuel, get bigger jobs done faster without the usual hassles. Scientifically engineered to outperform fishing line; withstands concrete and fences, slashes heavier vegetation, cuts grass cleaner with lift, and blows debris. For Gas Trimmers only does not fit electric or battery powered trimmers.