XHT (Xtreme Hardness & Toughness) blades feature a unique steel that incorporates boron, carbon, manganese, and other materials that ensure its strength. The blades are heat treated with the patented and independently tested Marbain heat-treating process. This process makes the blades 25% - 40% harder than standard lawnmower blades, making them the longest-lasting, safest, and most impact resistant lawnmower blades on the market. Sold individually. 3 required per application.     Dim E (5): XHT     Dim F (6): 3 Blades Used For 60" Cut     Center Hole: 1.125"     Length: 20.500"     Replaces: K5647-34330, K5647-34340     Thickness: .250"     Width: 2.500"