QualityParts From Oregon That you can depend on. Center hole: 15/16": Requires 3 blades for 50" 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; Made to exact OEM specifications; Tungsten carbide is “fused” into the blade – creating an ultra-hard layer at the cutting edge and increasing the time between sharpening. Oregon Equipment Parts 492-731 Blade Exmark 17-1/2 In - Fusi