XHT blades are made from the highest grade of steel for the best cutting and performance money can buy. With the best hardness, strength, and durability in the market, this range of blades is recommended for every mower in the market. They are stronger, harder, and last longer in any environment. HT 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! This sale is for 3 replacement XHT blades. Replaces the following OEM part numbers: JOHN DEERE TCU30316 M136195 Center Hole: 7/8" Width: 2-1/2" Thickness: .250" Length: 19"