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! This sale is for 3 replacement XHT blades. Replaces the following OEM part numbers: JOHN DEERE TCU30317 M144652 M136195 M135334 Blade specs Center hole: 7/8" Width: 3" Thickness: .250" Length: 19" 3 BLADES FOR 54" CUT HIGH LIFT Z-TRAK Z710A,Z810A,Z820A,Z830A,Z840A,Z850A,Z910A,Z915B,Z920A,Z920M,Z920R,Z925A,Z930A,Z930M,Z950A,Z960A,Z970A,647A,657,657A,667A,717A,727,727A,737,757 *DISCLAIMER- WE LIST BLADE PART NUMBERS, MODEL NUMBERS AND DIMENSIONS FOR REFERENCES BUT IT IS UP TO YOU TO BUY THE RIGHT BLADES. You will receive the blade that match the dimensions above.