John Deere GY20679 54" Replacement mower blades OEM Part Numbers: GY20679 / GX21380 / GY20684 / GY20686 Replaces OEM Part Number(s): John Deere lawn mower blades are manufactured with a combination of carbon and boron to provide hardness for a long life and sharp edge without breakage. Includes Lock Nuts X3 and Blades X3