Ferris OEM Replacement Blade 302-821
Requires 3 for 61'' deck; toothed blade 
Lenght 21'' (533.4mm) 
Centre Hole 5/8'' (15.9mm)
Outer Hole 3/8'' (9.5mm)
Centre 4'' (101.6mm)
Width 2 1/2'' (63.5mm)
Thickness .250'' (6.4mm)