Weedwakka™ Heavy Duty will cut a wide range of vegetation, from light grass to blackberries, including woody weeds with stems to thumb thickness. Replaces steel and plastic blades. (b) Hardened steel blades cut efficiently and never require sharpening. (b) The articulated blade design absorbs shock when a solid object is struck. PLEASE NOTE!: Both Weedwakka™ models are designed for use on STRAIGHT SHAFT BRUSHCUTTERS ONLY and must not be used with any other type.