DR DuraBlades are perfect for cutting woody brush that is too tough for your cutting cords, and too flexible and “whippy” for the Beaver Blade. To attach the DuraBlades simply unscrew your Mow-Ball and replace it with the new, Mow-Ball/DuraBlade holder. Includes new Mow-Ball mounted with 3 blades, plus an extra set of 3 blades.