SET OF 2 - SUNBELT BLADE-MOWER, 21", 3/4", MULCH - B1CC1425 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. (2) blades for 42" cut. Center Hole: 3/4" C to C: 2.5" Length: 21" Outer Hole: 5/16" Thickness: .165 Type: Highlift Width: 2-3/4" This is an Aftermarket part. Thanks for looking!