XHT Stands for Xtreme Hardness and Toughness. XHT starts with the steel. All XHT Blades feature a unique steel that incorporates boron, manganese, and other materials that ensure strength. The final step in the XHT process is patented and independently tested Marbain heat-treating process. This process makes XHT blades approximately 25% - 40% harder than standard lawnmower blades, making them the longest lasting, safest, and most impact resistant blade on the market. The Benefits of XHT blades include: Cutting edge stays sharper, longer Wear resistance in the most strenuous conditions Impact Toughness Resistance to bending Tightest tolerances in the aftermarket vs. OEM