Oregon 91-253 Heavy Duty Blade for 60 Gravely ZT HD 60 – 991279, 03253900. Blade Thickness – 0.250. Center Hole Size – 5/8. Air Lift – 1-1/8. You can count on the OregonĀ® 91-253 replacement lawn mower blade to be the best in the industry. It delivers a clean cut for quality results. Requires 3 blades for 60 cut. Resists bending, breaking and fracturing. Major brand replacement: Gravely. 025124, 046999, 08979600, 8979651. 25120, 36928, 37491, 37999, 38425, 38648, 40185, 40253, 41774, 42200, 43006, 43457, 45743, 45781, 45790, 45926, 47148, 47687. Listing and template services provided by inkFrog.