Universal Fit either 1" (25.4mm) or 20mm Arbor Hole sizing with your "Blade Hardware" You can measure "Washer" thickness with a Caliper, the Washer is the exact thickness of the blade and will even smash somewhat when firmly tightened
BLADE HARDWARE -- A Blade will Not fit onto the Trimmer Axle Shaft by itself like the String Line Dispenser Spool will. So you must acquire "Blade Hardware" that consists typically of two small discs; one has a raised circle,on it that the blade hole fits onto, the 2nd small disc is the cap disc, then screw on the Nut and apply a Cotter Pin. blade hardware is not included
Tungsten steel -- is estimated to last 10x longer than plain steel but does not cost 10x more creating incredible value. make for a better Tungsten steel for longer lasting teeth
Fit For A lot of straight shaft trimmers including Stihl Husqvarna Sears Husky Poulan shindaiwa Redmax Echo and Many others