Replacement mower blades by Oregon. These blades are made to exact OEM specification for optimum performance. Each blade is thru-hardened to a Rockwell C-scale hardness of 50 for optimum safety and durability, then individually straightened for a precision cut. All Oregon mower blades are made in the U.S.A.Blade Length 21-17/64" (54cm) Blade Width 4" (10.16cm)Blade Thickness .105" (2.66mm)Center Hole Diameter 23/32" (18.23mm)Outer Hole Diameters 13/32" (10.31mm)Distance Between Outer Holes 3-15/32" (88.08mm)Fits the Following Machines:Honda (1)21" Bottom BladeReplaces Honda Part Numbers 72511-VK6-000.