Master Mechanic, Dual, Fixed Speed Load, 2 Or 4 Line, Trimmer Head, Simple Line Replacement Action That Locks The Line At Any RPM, Head Is Well Balanced For Limited Vibrations, Low Profile Design Lets You Work Close To The Ground, Works With All Line Shapes & Sizes Up To .119", Universal Fit For Curved Or Straight Shaft Units, Includes Full Adaptor Kit, Fits All Known Brands.