REPLACEMENT XHT BLADES Extreme Hardness Toughness 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. By the way they are made in the USA! Hands down the ABSOLUTE best aftermarket replacement blade on the market! Don't waste your money on the cheapest set you can find on eBay unless you want a cheap blade that will not perform! STOP!! There are more than one style blade on the 54" cut machines. Some take the round center hole (like this) and others take a star hole. Know what you need before you buy. You are buying a set of 3 blades for GT & PRO midsize walk behinds and others that have the 54" deck. Center Hole: 3/4" round Width: 3" Thickness: .197" Length: 118-1/2"" Please make sure you are ordering the correct blades. We list model numbers, part number and the exact dimensions so you know exactly what you are getting. Just because the model number is not listed does not mean it doesn't fit but are because it is listed to mean it does. There are serial number breaks and other factors that sometimes change needed blades.