Honda OEM Replacement Blade 305-0369
FITS MODELS: HRX 537C-HRX, 537C1, HRX 537C2 AND IZY 53
Mulching blade 
Lenght 21'' (533mm)
Centre Hole 1 1/4'' 932mm)
Outer Hole 3 9/20'' (88mm) 
Centre 3/8'' (10.3mm)
Width 2 5/8'' (66mm)
Thickness 3/32'' (2.4mm)