Original equipment replacement 21-inch blade 532189028. This blade is a mulching blade. The ends of the blades were created to cut the grass and bring it into the deck where it is cut several more times before dispensing it back down. You will need a wrench to change the blade due to the blade bolt and nut needing to be removed.
The dimensions of this blade are:-21 inches long -2-1/4th wide -5/8th center hole To ensure a proper fit to your mower
Reference your owner’s manual or conduct a simple internet search of your mower’s model number.