QualityParts From Oregon That you can depend on. Center hole: 3/8": Requires 1 blade for 21" cut; For walk-behind mowers; Superior mulching for bagging and discharge efficiency; Enhanced hardening to keep the blade sharper and more durable; Made to exact OEM specifications; Replacement for major brands: Gravely, Huskee, and Ariens Oregon Equipment Parts 91-005 Blade Ariens/Huskee 20-9/16In[