These are the HC-155 20 inch blades. They were also sold with 24 inch blades, check your fitment and part number before ordering.

Part X411000700 (CUTTER 20")
Where Used:
· HC-155 S/N: S68011001001 - S68011999999-->Front Handle, Gear Case, Blades - 20" WITH Tip Guard
· HC-155 S/N: S68011001001 - S68011999999-->Front Handle, Gear Case, Blades - 20" WITHOUT Tip Guard
· HC-155 S/N: S76212001001 - S76212999999-->Front Handle, Gear Case, Blades - 20" WITHOUT Tip Guard
· HC-155 S/N: S76212001001 - S76212999999-->Front Handle, Gear Case, Blades - 20" WITH Tip Guard
· HC-155 S/N: S83713001001 - S83713999999-->Handle, Gear Case - 20" WITHOUT Tip Guard
· HC-155 S/N: S83713001001 - S83713999999-->Handle, Gear Case - 20" WITH Tip Guard