Lennox 25M53 Fan Blade 318973 401 secondary components like the specific secondary components like the specific gas orifice or ignitor should be transferred from the existing unit or purchased separately to match your specific gas type (Natural Gas or Propane) This part is a critical component for maintaining burner sequencing and preventing nuisance lockout codes in compatible forced air furnaces Attempting to ream the hub to fit a larger shaft will compromise the balance and integrity of the assembly The Lennox 25M53 Fan Blade is a precision engineered OEM replacement part designed for high performance heat rejection in residential condensing units