CastelGarden OEM Replacement Blade 305-0459
Left hand blade 
Length 16 9/16'' (420mm)
Centre Hole 11/16'' (18mm) 
Outer Holes 11/32'' (8.75mm)
Centre 2 9/16'' (65mm)
Width 2 3/8'' (55mm) 
Thickness 1/8'' (3mm)