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: KUBOTA K5619-34330 K5351-99040 Center Hole: 7/8" **MAKE SURE you have 7/8", Kubota has 3 different hole sizes in 54" cut machines!**** Width: 2-1/2" Thickness: .250" Length: 18-5/8" Kubota MOWER DECK: RCK54GR Kubota MOWER DECK: RCK54P-227Z Kubota MOWER DECK: RCK54P-321Z Kubota MOWER DECK: ZD321N **DISCLAIMER- WE LIST BLADE PART NUMBERS, MODEL NUMBERS AND DIMENSIONS FOR REFERENCES BUT IT IS UP TO YOU TO BUY THE RIGHT BLADES. If you order them and they don't fit it is not our fault! We always accept returns but the shipping to and from will be your responsibility unless we make the error.