CastleGarden OEM Replacement Blade 305-0449
Length 18 9/10'' (480mm)
Centre Hole 3/4'' (18.5mm)
Outer Hole 5/16'' (8.5mm)
Centre 2 1/8'' (54mm)
Width 3 5/32'' (80mm) 
Thickness 1/8'' (3mm)