PART NO. A-B1SC3801. BLADE-MOWER, XHT, 18″, 5/8″, NOTCH. 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.   (2) blades for 36″ cut. (3) blades for 52″ cut. Newer style blade w/ longer air lift. Center Hole 5/8″ Length 18″ Thickness .197 Width 2-1/2″. MODELS: Scag (Undefined): SEVERAL (36″ & 52″)