The Grass Gator Extra Heavy Duty replacement blades, part no. 4660 are designed for the Grass Gator Extra Heavy Duty trimmer head, part no. 4650. Do not use these blades on any replacement head other than the Grass Gator 4650. This replacement-Pack contains 3 tough stainless steel blades. The Grass Gator blades are easy to install and directions for installing the new blades are included on the-Package.