Description 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.(1) blade for 21" cut walk-behind.Specifications: Application: Mulching.C to C: 1-7/8".Center Hole: 5/8".Length: 21".Outer Hole: 3/8".Thickness: .134.Width: 2-1/4".