Honda OEM Replacement Blade 305-0709
Left hand mulching blade 
Length 18 3/16'' (46.2mm)
Centre Hole 3/4'' (18.5mm)
Outer Hole 11/32'' (8.5mm)
Centre 2 9/19'' (65mm)
Width 2 1/4'' (57mm)
Thickness 5/32'' (4mm)