(6 Pack) Stens Premium Replacement 21" x 2 &frac12;" Notched Lawn Mower Deck Blade | 310-078 310-086 310-185 315-872 This is a Brand New 6 Pack Premium Replacement Lawn Mower Deck Blade Top Quality Premium Replacement Replacement Part! Length 21" Width 2 " Thickness .197" Center Hole Diameter 5/8" 61" Cut Using 3 Blades Replacement XHT Lawnmower blade. XHT(Xtreme Hardness & Toughness) blades are 25-40% harder than standard lawnmower blades. Benefits of the HXT blade are sharper and longer lasting cutting edges. More resistance to bending. Tighter tolerances in the aftermarket vs. OEM. XHT blades also offer greater impact toughness.