QualityParts From Oregon That you can depend on. Center hole: 1/2": Requires 5 blades for 90" cut; Requires 7 blades for 124" cut; High-lift: The aggressive blade angle increases air flow to push debris up-and-out for superior bagging or side discharge.; Superior mulching for bagging and discharge efficiency; Enhanced hardening to keep the blade sharper and more durable; Fits Jacobsen models: AR-5, AR-522, and AR-722T Oregon Equipment Parts 91-591 Blade Jacobson 4137186 22-5/